- 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

- 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.

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.

which may be optionally overridden by version-specific rules.

For example the default rules for gcc on GNU/Linux x86_64 are in the
wmake/rules/linux64Gcc directory.  If there is a need to change any of
the rules for a specific version of gcc, e.g. gcc-4.8.4 the directory
wmake/rules/linux64Gcc48 may be created into which any of the language
files may be provided containing the rules to override the defaults.

The c++0x is used rather than c++11 to support gcc-4.5.?

Also removed __GNUC__ conditional compilation statements which are no
longer needed.

Tested with snapshot gcc-5-20150215.tar.bz2

- To-do:
      wmake/rules/General/bison
      wmake/rules/General/btyacc
      wmake/rules/General/btyacc++
      wmake/rules/General/byacc
      wmake/rules/General/moc
      wmake/rules/General/yacc

  but these files have <TAB>

COMP: Fedore13 has linkage with --no-add-needed as default. This disallows indirectly loaded libraries.

- main mplib rules located in GENERAL_RULES with specializations
  (if any) under RULES. Modest change in a few options files, but
  cleans up the rules directories.

  previously in options:
      include $(RULES)/mplib$(WM_MPLIB)

  now in options:
      sinclude $(GENERAL_RULES)/mplib$(WM_MPLIB)
      sinclude $(RULES)/mplib$(WM_MPLIB)

  For GNU make it would be permissible to write both in a single line.

- otherwise /lib/cpp may need a different library binding than
  currently available and results in this type of error:

  /usr/lib64/gcc/x86_64-suse-linux/4.4/cc1:
  /data/app/OpenFOAM/ThirdParty-1.6.x/platforms/linux64/gcc-4.3.3/lib64/libstdc++.so.6:
  version `GLIBCXX_3.4.11' not found (required by
  /usr/lib64/libppl_c.so.2)

ENH: remove unused flex++ rule for SiCortex that was identical to the
general one anyhow.

ENH: generalize rule for X11

ENH: Avoid move in flex/flex++ rule.

This signals that we are using the system installed openmpi version.

This reverts commit 5050e9e6.

-lrt nor needed in src/decompositionMethods/decompositionMethods/Make/options