- now use debug 2 for scanner and debug 4 for parser.
  Provided better feedback about what is being parsed (debug mode)

- relocate debug application to applications/tools/foamExprParserInfo

- an empty WM_COMPILE_OPTION is treated internally (in make rules)
  like "Opt"

- an empty WM_COMPILER_TYPE is treated like "system" (system compiler)

- locate where the user is less tempted to change it (#1515).
  It really should be considered an invariant environment variable.

STYLE: wmake -help information to stdout, die errors to stderr

- skip processing OSspecific/MSwindows since this can cause duplicate
  doxygen entries

STYLE: adjust formatting in code templates

STYLE: use std::string methods without extra qualifications

- when using VTK from ParaView sources it can better to tag them as
  such, but simultaneously not mask the ParaView with hardware
  rendering.

  The additional ParaView_MESA_DIR variable allows this.
  The balance of library and path setup is unaffected by this.

DOC: update doc/BuildIssues

- no stderr redirect needed:
    * 'command -v'

- no stdout/stderr redirect needed:
    * 'rm -f'

STYLE: consistent spacing after redirects

- this can help if using std algorithms that return a const reference
  such as std::min() does.

- adjust known gcc/clang compiler versions

- call also be used non-interactively for simple 'one-shot' use of
  OpenFOAM utilities or solvers

STYLE: use dash instead of brackets for '- see www.OpenFOAM.com'

- less cluttered in combination with API information

CONFIG: remove adios1 config files

- the use of 'paraview --version' can be fail if the build host
  doesn't have the necessary graphics. For this case, try to obtain
  the ParaView API number from the associated include directory.

- with 1906, OpenFOAM is purely C++ code and the last toolchain bits C
  code have been avoided. Thus relax the wmake C rule for including
  WM_COMPILE_OPTION. This makes it much easier to add different
  compiler options with fewer files.

  For example, for Broadwell-specific options:

      cd wmake/rules/linux64Gcc
      cp c++Opt c++OptBdw

      edit this file and then use WM_COMPILE_OPTION=OptBdw

- ensure that WM_COMPILE_OPTION is always non-empty

- makes the standard config variables more visible

- this cannot be left as a configurable value (on windows), since it
  needs to be enabled even prior to reading the etc/controlDict file,
  in case the OpenFOAM installation path itself contains spaces.

Caveat: The -Wdeprecated-copy produces many, many compiler warnings