- "buffered" corresponds to MPI_Bsend (buffered send),
  whereas the old name "blocking" is misleading since the
  regular MPI_Send also blocks until completion
  (ie, buffer can be reused).

ENH: IPstream::read() returns std::streamsize instead of label (#3152)

- previously returned a 'label' but std::streamsize is consistent with
  the input parameter and will help with later adjustments.

- use <label> instead of <int> for internal accounting of the message
  size, for consistency with the underyling List<char> buffers used.

- improve handling for corner case of IPstream receive with
  non-blocking, although this combination is not used anywhere

Fix fvsPatchFields reading/writing the "value" entry

See merge request Development/openfoam!679

- robuster and more reliable determination of inserted objects
  (previous code could produce false positives).

  Now also determine the number of inserted objects within the
  constructor (instead of simply storing a bool). This allows reuse
  in the address calculations to reduce overheads there.

BUG: dodgy short-circuit logic for insertedObjectLabels()

- as a quick short-circuit it previously created as demand-driven
  pointer with a zero elements. However, this meant that if this code
  was called first (before any other addressing), subsequent calls to
  the addressing would fail.

BUG: bad logic and lookup for faAreaMapper (#3147)

- was using labelHashSet but returning a bool and set using the
  addressing using the unfiltered objects!
  This is a latent bug since interpolated/inserted faces not
  currently supported anyhow.

ENH: use std::unique_ptr for demand-driven data

- manual revert for 44d0fbd5.

  Unless required for post-processing the "value" entry should not
  written if it is not mandatory for reading.

  This is especially crucial with an 'empty' patch field where the
  field (size 0) has a different size from the patch.

- the changes made align fvsPatchField behaviour with fvPatchField

- return autoPtr<token::compound> instead of the derived type,
  otherwise cannot easily construct a token from it

ENH: additional typed version of refCompoundToken()

- symmetric with typed version of transferCompoundToken()
  and isCompound()

- add ITstream::findCompound<Type>() method.
  Useful for searching within token streams

reduce communication argList at startup

See merge request Development/openfoam!678

- previously automatically skipped the first communicator (which was
  assumed to be MPI_COMM_WORLD), but now simply rely on the
  internal pendingMPIFree_ to track which communicators have actually
  been allocated.

- UPstream::Communicator is similar to UPstream::Request to
  wrap/unwrap MPI_Comm. Provides a 'lookup' method to transcribe
  the internal OpenFOAM communicator tracking to the opaque wrapped
  version.

- provide an 'openfoam_mpi.H' interfacing file, which includes
  the <mpi.h> as well as casting routines.

  Example (caution: ugly!)

     MPI_Comm myComm =
         PstreamUtils::Cast::to_mpi
         (
             UPstream::Communicator::lookup(UPstream::worldComm)
         );

- replace point-to-point transmission of the argList args/options with
  a broadcast. This is sufficient for most cases (without distributed
  roots).

  For "normal" cases (non-distributed roots) this will replace the
  nProcs-1 messages with a single broadcast.

- for cases with distributed roots, distinguish between a single,
  identical root and different roots.  An identical root can also be
  subsequently handled with a broadcast. Different roots will still
  require individual point-to-point communication.

  For cases with distributed roots, it will add the overhead of an
  additional broadcast.

- adds consistency with regular point-to-point parallel streams.

ENH: add ITstream::tokens() methods

- useful, for example, to disambiguate constructing tokenList from
  a ITstream.

  ITstream& is = otherDict.lookup("original");

  tokenList deepCopy(is);  // Error: from Istream or tokenList??
  tokenList deepCopy(is.tokens());  // OK: from tokenList

- same as append() did, but with more consistent names

STYLE: replace special purpose append() with container method

STYLE: update code style

update to internal accounting for finite-area

See merge request Development/openfoam!675

- The internal storage location of finite-area changes from being
  piggybacked on the polyMesh registry to a having its own dedicated
  registry:

  * allows a clearer separation of field types without name clashes.
  * prerequisite for supporting multiple finite-area regions (future)

Old Locations:
```
   0/Us
   constant/faMesh
   system/faMeshDefinition
   system/faSchemes
   system/faSolution
```

New Locations:
```
   0/finite-area/Us
   constant/finite-area/faMesh
   system/finite-area/faMeshDefinition  (or system/faMeshDefinition)
   system/finite-area/faSchemes
   system/finite-area/faSolution
```

NOTES:
    The new locations represent a hard change (breaking change) that
    is normally to be avoided, but seamless compatibility handling
    within the code was found to be unworkable.

    The `foamUpgradeFiniteArea` script provides assistance with migration.

    As a convenience, the system/faMeshDefinition location continues
    to be supported (may be deprecated in the future).

- was using blocking (=buffered) comms
- was running out of MPI_COMM_SIZE buffer space
- now using PstreamBuffers to have non-blocing comms

- lower memory overhead, consistent access pattern

- use an internal 'typedef MeshObject<...> MeshObject_type' within
  derived classes. Reduces clutter and eases any updates.

- Delete() will perform a 'checkOut()' which does the following:
  * remove the object from the registry
  * delete the pointer (if owned by the registry)

- Release() does the following:
  * transfer ownership of the pointer (if owned by the registry)

- Store() does the following:
  * transfer ownership of the pointer to the registry

ENH: use UPtrList of sorted objects for MeshObject updates

- few allocations and lower overhead than using a HashTable,
  ensures the same walk order over the objects (in parallel)

STYLE: adjust meshObject debug statements

STYLE: update code style for phi modification (engine motion)

ENH: pass isMeshUpdate param in fvMesh/polyMesh clearOut() methods

- top-level use of isMeshUpdate parameter to clearOut and
  clearAddressing was being inadvertently filtered out

- after the modification of d578d48a, the parent was now actually
  searched. However, should be returning "constant" and not trigger a
  FatalError if the file/directory is not found.

- findStrings, findMatchingStrings now mostly covered by matching
  intrinsics in wordRe and wordRes.

  Add static wordRes match() and matching() variants

COMP: remove stringListOps include from objectRegistry.H

- was already noted for removal (NOV-2018)

- an example of the new, more succinct refConstCast version:

      auto& abc = refConstCast<adjointVectorBoundaryCondition>(Uab);

  older:
      adjointVectorBoundaryCondition& abc =
          refCast<adjointVectorBoundaryCondition>
          (
              const_cast<fvPatchVectorField&>(Uab)
          );
  or:
      adjointVectorBoundaryCondition& abc =
          const_cast<adjointVectorBoundaryCondition&>
          (
              refCast<const adjointVectorBoundaryCondition>(Uab)
          );

- an example of the new, more succinct isA_constCast version:

      auto* acapPtr = isA_constCast<fieldType>(abf[patchi]);

      if (acapPtr)
      {
          auto& acap = *acapPtr;
          ...
      }

  older:
      if (isA<fieldType>(abf[patchi]))
      {
          fieldType& acap =
              const_cast<fieldType&>
              (
                  refCast<const fieldType>(abf[patchi])
              );
          ...
      }

STYLE: remove spurious 'const' qualifier from isA<> use

- NewIFstream would read complete remote file to decide if
  was collated.
- This limits files to 31bit size
- Instead now have master-only opening of file.
- Still has problem with refinement history/cellLevel etc.

- previously would always return "constant" as the instance for
  an optional dir/file that wasn't found.
  However, this meant retesting to screen out false positives.
  Now support an additional parameter
      'bool constant_fallback = ...'
  to return "constant" or an empty word.

  The method signature changes slightly with a new optional bool
  parameter:

      //! Return \c "constant" instead of \c "" if the search failed
      const bool constant_fallback = true

ENH: code consolidation for findInstancePath

- relocate from Time to TimePaths and provide an additional static
  version that is reused in fileOperations

BUG: distributedTriSurfaceMesh:::findLocalInstance broken (#3135)

- was not checking the parent at all.

COMP: remove unused findInstancePath(const fileName&, ..) method

- support construct faceZoneSet from faceSet (#3126)

ENH: support unregistered loading of cell/face/point sets

- leave 'readContents' method name for exposed (public) methods.
  Generally not a problem, but can confuse the compiler when various
  public/private versions are available with the same number of
  parameters.

STYLE: adjust meshObject debug statements

- regIOobject::store(std::unique_ptr<...>&& ptr)
- IOobjectList::add(std::unique_ptr<...>&& ptr)

STYLE: io.globalCaseName() instead of io.time().globalCaseName() [#3007]

ENH: combine broadcasts for uncollated master-only handling

- the rootProcNo is usually == UPstream::masterNo()

- the type/name for field caching were saved as word, but ensight has
  things like "tensor symm" etc, which do not parse very well as
  'word'. Now save as 'string' type.

  Backwards compatibility is OK since a word token will also be
  readable as string etc.

- makes string reading consistent with fileName reading.

  Related to #3133 to also allow compatibility when reading existing
  dictionaries written with unquoted string contents.

- used defunct "processors/" directory naming, and includes are now
  addressed by the file-handler anyhow.

ENH: support 'tutorials/Alltest -init'

- for copying/creating test directory without running