- The iterator for a HashSet dereferences directly to its key.

- Eg,

      for (const label patchi : patchSet)
      {
          ...
      }
  vs.
      forAllConstIter(labelHashSet, patchSet, iter)
      {
          const label patchi = iter.key();
          ...
      }

Feature regionsplit

See merge request OpenFOAM-plus!201

    No completion added for XXX
    ... incorrect platform, or not yet compiled?

- the algorithm was last used in OpenFOAM-2.4, after which it was
  replaced with a FaceCellWave version.

  Whereas the original (2.4.x) version exhibited performance
  degradation on very large meshes (with explicit constraints), the
  FaceCellWave version exhibited performance issues with large numbers
  of blocked faces.

  With large numbers of blocked faces, the FaceCellWave regionSplit
  could take between 10 to 100 times longer due to the slow
  propagation speed through blocked faces.

  The 2.4 regionSplit has been revamped to avoid local memory
  allocations, which appears to have been the source of the original
  performance issues on large meshes.

  For additional performance, intermediate renumbering is also avoided
  during the consolidation of regions over processor domains.

- controlled by the the 'printExecutionFormat' InfoSwitch in
  etc/controlDict

      // Style for "ExecutionTime = " output
      // - 0 = seconds (with trailing 's')
      // - 1 = day-hh:mm:ss

   ExecutionTime = 112135.2 s  ClockTime = 113017 s

   ExecutionTime = 1-07:08:55.20  ClockTime = 1-07:23:37

- Callable via the new Time::printExecutionTime() method,
  which also helps to reduce clutter in the applications.
  Eg,

     runTime.printExecutionTime(Info);

  vs

     Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
         << "  ClockTime = " << runTime.elapsedClockTime() << " s"
         << nl << endl;

--

ENH: return elapsedClockTime() and clockTimeIncrement as double

- previously returned as time_t, which is less portable.

- reduce cell looping. Avoid initial looping over blockFace.

- make early return (no processor sets, connections, or blocked faces)
  more apparent.

- alternative calcCellCells that handled explicitConnections was
  deactivated (2014 or earlier) and finally removed APR-2018.

For example, with some HashTable or Map container of models

    { model0 => 1, model1 => 4, model2 => 5, model3 => 12, model4 => 15, }

specify the remapping

    Map<label> mapper({{1, 3}, {2, 6}, {3, 12}, {5, 8}});

inplaceMapValue(mapper, models) then yields

    { model0 => 3, model1 => 4, model2 => 8, model3 => 12, model4 => 15, }

--

ENH: extend bitSet::count() to optionally count unset bits instead.

--

ENH: BitOps compatibility methods for boolList.

- These ease coding that uses a boolList instead of bitSet and use
  short-circuit logic when possible.

  Eg, when 'bitset' and 'bools' contain the same information

      bitset.count()  <->  BitOps::count(bools)
      bitset.all()    <->  BitOps::all(bools)
      bitset.any()    <->  BitOps::any(bools)
      bitset.none()   <->  BitOps::none(bools)

  These methods can then be used directly in parameters or in logic.
  Eg,

      returnReduce(bitset.any(), orOp<bool>());
      returnReduce(BitOps::any(bools), orOp<bool>());

      if (BitOps::any(bools)) ...

- bitSet::used() method for compatibility with code using the
  PackedBoolList typedef, but marked as deprecated.

- with updated DynList that inherits from UList and uses List/FixedList
  internally for its memory management

- since PackedBoolList is now a compatibility typedef for bitSet,
  it is useful to have an additional means of distinction.

STYLE: simplify internal version tests and compiler defines.

- the API version is now conveyed via the OPENFOAM define directly.
  The older OPENFOAM_PLUS define is provided for existing code.

- parsing error state only arises from a missing final newline
  in the file (which the dnl macro does not capture).
  Report with a warning instead of modifying the dnl macro since
  we generally wish to know about this anyhow.

- add missing newline to YEqn.H file.

ENH: new bitSet class and improved PackedList class (closes #751)

See merge request OpenFOAM-plus!200

- flags the following type of problems:

  * mismatches:

        keyword  mismatch ( set of { brackets ) in the } entry;

  * underflow (too many closing brackets:

        keyword  too many ( set of ) brackets ) in ) entry;

- a missing semi-colon

        dict
        {
           keyword  entry with missing semi-colon
        }

  will be flagged as 'underflow', since it parses through the '}' but
  did not open with it.

Max monitoring depth is 60 levels of nesting, to avoid incurring any
memory allocation.

- handling of dead links (find -L -delete unsupported)

- remove ignore case flag on 's/../../i' used in have_scotch script.
  It is unneeded and not tolerated by Darwin's sed.

- avoid embedded comments in EXE_INC (Make/options files), which do
  not work well with the OSX LLVM cpp.
  It strips out the comments but also removes the continuation char.

STYLE: adjust notes about paraview library locations

- size ambiguity for Foam::min(string::size_type, label)

- stream operators for int16/uint16 which are needed for mode_t (Darwin)

- was somewhat redundant in wmake/rules/General/general anyhow

- generalize some of the library extensions (.so vs .dylib).
  Provide as wmake 'sysFunctions'

- added note about unsupported/incomplete system support

- centralize detection of ThirdParty packages into wmake/ subdirectory
  by providing a series of scripts in the spirit of GNU autoconfig.
  For example,

      have_boost, have_readline, have_scotch, ...

  Each of the `have_<package>` scripts will generally provide the
  following type of functions:

      have_<package>          # detection
      no_<package>            # reset
      echo_<package>          # echoing

  and the following type of variables:

      HAVE_<package>          # unset or 'true'
      <package>_ARCH_PATH     # root for <package>
      <package>_INC_DIR       # include directory for <package>
      <package>_LIB_DIR       # library directory for <package>

  This simplifies the calling scripts:

      if have_metis
      then
          wmake metisDecomp
      fi

  As well as reducing clutter in the corresponding Make/options:

      EXE_INC = \
          -I$(METIS_INC_DIR) \
          -I../decompositionMethods/lnInclude

      LIB_LIBS = \
          -L$(METIS_LIB_DIR) -lmetis

  Any additional modifications (platform-specific or for an external build
  system) can now be made centrally.

- permits platform-specific override of the general CGAL rules

- also simplify parsing by accepting any case on keywords.
  This implies that something like "sOlId", "SoLiD" will also
  be accepted. Although nobody should really count on this rather
  generous behaviour, it does simplfy the state machine even further.

STYLE: change access methods names in mesh wave algorithms

- nUnvisitedCells(), nUnvisitedFaces() etc instead of
  getUnsetCells(), getUnsetFaces()

- simplify some coding with range-for

- in 2.4.x the general default for polyMesh::findCell was FACE_DIAG_TRIS,
  but this was changed to CELL_TETS for better handling of concave
  cells.

- in snappyHexMesh meshRefinement, findCell is used to define
  locations in mesh and cells for closer refinement. Using CELL_TETS
  causes an octree rebuild when the mesh has changed and this adds
  considerable overhead. For this operation, the faster FACE_DIAG_TRIS
  mode can be used instead.

- the previous grammar used

      '/*' { fgoto comment; }

  to start processing multi-line comments and

      comment := any* :>> '*/' @{ fgoto main; };

  as a finishing action to return to normal lexing, but seemed not to
  have been triggered properly.

  Now simply trap in a single rule:

      '/*' any* :>> '*/';             # Multi-line comment

STYLE: use more compact dnl (delete to newline)

  OLD:   [^\n]* '\n'
  NEW:   (any* -- '\n') '\n'

  eliminates the intermediate state

- the API-versioned calls (eg, tecini142, teczne142, tecpoly142, tecend142),
  the limited availability of the SDK and lack of adequate testing make
  proper maintenance very difficult.

- in debug, also report the first 10 cell ids

- format header documentation