- In addition to the traditional Flex-based parser, added a Ragel-based
  parser and a handwritten one.

  Some representative timings for reading 5874387 points (1958129 tris):

      Flex   Ragel   Manual
      5.2s   4.8s    6.7s         total reading time
      3.8s   3.4s    5.3s         without point merging

- better naming consistency with std::regex_constants::icase

- deprecate older NOCASE, but leave supported

- now uses current OpenFOAM code level

- added initial catalyst script for insitu processing of overset

- note that the python paths also seem to be treated differently

- However, the new ragel-based parser is much faster
  than the others, and does not cause 'too many open files' error
  that the flex-based parser does (issue #784).

  The timings (using src/sampling as being somewhat representative)

    $ wclean; wmakeLnInclude -u .; time wmake -s dep

        3.4s  wmkdepend (ragel) [now default]
        5.7s  wmkdep (flex)
        6.1s  cpp -M

- The makeDepend script is for testing purposes only, but could used as
  a hook for other dependency generation systems (eg, ninja).
  It simply wraps 'cpp -M' in a form that is calling compatible with
  wmkdepend.

BUG: wmkdepend parser was missing optional leading space on #include match

STYLE: use -G2 (goto-based) option for wmkdepend state machine

- the machine is compact with few states and lends itself to this

- the expansions were previously required as slash to follow, but
  now either are possible.

    "<case>", "<case>/" both yield the same as "$FOAM_CASE" and
    will not have a trailing slash in the result. The expansion of
    "$FOAM_CASE/" will however have a trailing slash.

- adjust additional files using these expansions

- make purpose as functors _slightly_ clearer.

- base definition removed for stricter enforcement of the specialization
  requirement.

- a partial selection from https://github.com/mrklein/openfoam-os-x
  with adjustments. The primary purpose is to reduce header-level
  incompatibilities and to provide a common set of make rules to allow
  easier patching (or re-integration).

Feature wmake

See merge request OpenFOAM-plus!198

  This is similar to efforts (Feb 2010) but using ragel
  (https://en.wikipedia.org/wiki/Ragel) instead of the now defunct
  coco/r. The modified commit message from 2010:

ENH: add C++-based wmkdepend parser (uses ragel grammar).

- This avoids dependency on lex/flex and provides better encapsulation
  for buffer switching. As a result, the maximum number of open files
  only corresponds to the include depth.

--

Note that the flex source and rules are still available, but are not
deactivate (see wmake/rules/General/transform)

Support the following expansions when they occur at the start of a
string:

    Short-form       Equivalent
    =========       ===========
      <etc>/          ~OpenFOAM/   (as per foamEtcFile)
      <case>/         $FOAM_CASE/
      <constant>/     $FOAM_CASE/constant/
      <system>/       $FOAM_CASE/system/

These can be used in fileName expansions to improve clarity and reduce
some typing

     "<constant>/reactions"   vs  "$FOAM_CASE/constant/reactions"

  ParaView 5.4 and older:
    - requires lib/paraview-X.X only

  ParaView 5.5:
    - requires lib/
    - does not appear to require lib/paraview-X.X, but retained for simplicity

- Change default version to paraview-5.5.0 for testing purposes

- this removes an OS-specific dependency (eg, drand48_r is not POSIX)
  and allows easier use of other random number generators.

  The Rand48 generator has identical behaviour and period as the
  lrand48() library routine, but holds its own seed and state
  (which makes it re-entrant) and can be combined with other
  random distributions.

  However, when using the modified form to obtain scalar values
  they will not be identical to what drand48() yields.

  This is because drand48() uses the raw 48-bit values to directly
  set the mantissa of an IEEE double where as the newer distribution
  normalizes based on the 32-bit value.

STYLE: simplify code in Random::shuffle and use Swap

- quick ignore of empty filenames.

- relocated some implementation details from POSIX.C to the
  fileStat class, where they make more sense.

- was using st_atim instead of st_mtim for the nanoseconds

- value of followLink was being ignored (it was always being followed).

- less efficient and less portable than using single-pass processing

This thermo is used with multiComponentMixture in rhoThermo type

keeping chocked conditions of Mach number.
This BC can work in two modes, chocked or non-chocked. In the
chocked mode the Ma is an input. In the non-chocked mode
the Ma is calculated from model inputs.

STYLE: use 'return nullptr' for empty autoPtr/tmp returns

See merge request OpenFOAM-plus!197

more consistent use of dimensioned Zero

See merge request OpenFOAM-plus!196

Feature catalyst

See merge request Development/OpenFOAM-plus!195

- this can occur when OpenFOAM is run in serial mode, but connects to
  a program that starts/stops MPI on its own.

- makes the meaning clearer