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

- Could be related to interrupted builds.
  So if there are any parts of the build that rely on an explicit
  'wmakeLnInclude', make sure that the contents are properly updated.

--

ENH: improved feedback from top-level Allwmake

- Report which section (libraries, applications) is being built.

- Provide final summary of date, version, etc, which can be helpful
  for later diagnosis or record keeping.

- The -log=XXX option for Allwmake now accepts a directory name
  and automatically appends an appropriate log name.
  Eg,
      ./Allwmake -log=logs/  ->> logs/log.linux64GccDPInt32Opt

  The default name is built from the value of WM_OPTIONS.

--

BUG: shell not exiting properly in combination with -log option

- the use of 'tee' causes the shell to hang around.
  Added an explicit exit to catch this.

--

- Detecting the '-k' (-non-stop) option at the top-level Allwmake, which
  may improve robustness.

- Explicit continue-on-error for foamyMesh (as optional component)

- unify format of script messages for better readability

COMP: reduce warnings when building Pstream (old-style casts in openmpi)

- 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.