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

- 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

- 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

Resolves bug-report http://bugs.openfoam.org/view.php?id=2283

- CGAL itself includes its library dependencies, we only need to
  provide the -L... option to the proper ThirdParty locations.

  Should help improve general build robustness.

- 64-bit builds of gcc/mpfr/gmp use lib64/ for their installation path.
  Use this for the wmake rules as well.

Patch contributed by Paul Edwards, Intel.

The change from C++0x to C++11 allows all of C++11 functionality to be
used in OpenFOAM, in particular constructor delegation which avoids code
duplication or constructor helper functions.  However, this also means a
change to the minimum gcc version supported which is now 4.7 rather than
4.5.

Note that gcc-4.7 does not support the entire C++11 standard but does
support all of the functionality currently needed for further OpenFOAM
development.  The minimum gcc-version which supports the entire C++11
standard is 4.8 which is now the recommended minimum gcc version.

The pre-processor macro 'OPENFOAM_PLUS' is defined with a numerical
value equal to the currently compatible version number.

This can be used judiciously within user coding to help with minor
differences between OpenFOAM versions. For example,

    #ifdef OPENFOAM_PLUS
        #if (OPENFOAM_PLUS >= 1612)
        ...
        #endif
    #endif

or simply

    #if (OPENFOAM_PLUS >= 1612)
    ...
    #endif