- comments
- avoid egrep for getting processor count.
- wcleanBuild, wcleanPlatform with shorter form '-curr' instead of '-c'
  to avoid any potential user confusion with '-comp'

- add -compiler=NAME option to remove a build or platforms directory
  corresponding to any specified compiler on the current arch.

- when -compiler or -compiler=NAME is specified, also clean related
  sub-directories as well. This will cleanup mpi-related directory.

- new behaviour is to do nothing if no platform was specified.
  This helps avoid inadvertently removing files.

- support special platforms for compatibility with wmake/wclean targets.
  Eg, "wcleanPlatform all"

- allow use from ThirdParty top-level as well, since the directory
  structure is similar.

BUG: fix regression in wcleanLnIncludeAll introduced by 9e2e1115

- use -name test before -type test to avoid calling stat(2) on every file.
- use -delete instead of -exec rm to avoid forking

- reduces unexpected interactions between various make elements

- also add some comments about the side-effects

The Makefiles are now in the makefiles sub-directory

The "-f | -force" option in wmakeLnInclude is now "-u | -update" for
consistency with the other scripts.

The "Usage" entry in the headers is now consistently formatted in all
scripts.

wcleanPlatform is a more general and cleaner version of wcleanMachine
supporting the "-all" option to provide the equivalent of wcleanAll.

Both wcleanMachine and wcleanAll are now deprecated and will be removed
for the next major release.