- this is consistent with compiler defaults, and helps Darwin users

- tie the MPI rules to the base compiler type *without* its version.
  Eg, linux64Gcc (which exists) instead of linux64Gcc81

- improvement documentation for surface sampling.

- can now specify alternative sampling scheme for obtaining the
  face values instead of just using the "cell" value. For example,

      sampleScheme    cellPoint;

  This can be useful for cases when the surface is close to a boundary
  cell and there are large gradients in the sampled field.

- distanceSurface now handles non-closed surfaces more robustly.
  Unknown regions (not inside or outside) are marked internally and
  excluded from consideration. This allows use of 'signed' surfaces
  where not previously possible.

- 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.

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

- permits platform-specific override of the general CGAL rules

- 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

- 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).

  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)

- easier to ensure that flags are consistent

- downgrades some diagnostics about nonconformant code from errors to
  warnings. Oddly enough, the errors actually arise from STL library
  elements shipped with gcc itself. Affects kahip compilation with
  gcc-6, gcc-7

- primary points for an external user are the polyMesh constructor

- add config info for gcc-7.3.0

COMP: intel-2017. Ignore unknown pragmas. Disambiguate method resolution.

- required if there is no system openmp and libomp or libgomp are
  only found in the clang hierarchy

STYLE: add some notes in the openmp rules.

- the _OPENMP macro is now used in low-level testing files

- allows enabling new warnings without causing messy output with older
  clang versions

- initial settings for ADIOS2, linuxARM64Gcc, linuxARM64Clang

- the USE_OMP preprocessor symbol is also defined with the openmp
  compile flag to allow conditional compilation of openmp-specific
  code.

- improve functional compatibility with DynList (remove methods)
  * eg, remove an element from any position in a DynamicList
  * reduce the number of template parameters
  * remove/subset regions of DynamicList

- propagate Swap template specializations for lists, hashtables

- move construct/assignment to various containers.

- add find/found methods for FixedList and UList for a more succinct
  (and clearer?) usage than the equivalent global findIndex() function.

- simplify List_FOR_ALL loops

- the cray C/C++ compilers appear to be option-compatible with gcc.

- no wmake rules for 32bit builds (deemed to be unnecessary)

- not yet release, but some of the API and file locations are closer
  to 1706 than to 1612. Needed, for example, for swak4foam.

- minor cleanup of wmake sources

- easier to test or use different versions

- change WM_CXXFLAGS to -std=c++11 instead of -std=c++0x

- use "-pvMAJ.MIN" suffix for similarity with the paraview convention

- use sentinel file to ensure clean change of intermediate targets

- ensure all library files are being properly removed

- slightly odd. Building CGAL on other Linux systems have a proper
  ldd dependency for gmp/mpfr, but ubuntu doesn't

- now that adios_config flags are largely working in ThirdParty

- support gperftools-none, gperftools-system configurations
  as per other third-party packages.

STYLE: clean up more environment variables

CONFIG: testing adios rule

- these directories are sometimes used for a central, non-thirdparty, non-system
  installation

- leave gmp and mpfr as is, since it is not clear how these would interact with system
  versions

Based on patch contributed by Alexey Matveichev
Resolves feature request http://bugs.openfoam.org/view.php?id=2328

On 64-bit systems, the system installations of boost, cgal are under
lib64/. The behaviour for a ThirdParty build is mostly lib/ but this
can also be changing.

    Boost 1_62_0 and older build into 'lib/'.
    CGAL-4.9 builds into 'lib64/', older versions into 'lib/'.

Future-proof things by using lib$WM_COMPILER_LIB_ARCH for boost and
cgal build rules, and forcing these as build targets in the ThirdParty
makeCGAL as well.

--
STYLE: check for boost/version.hpp, CGAL/version.h instead their directories