ENH: handle command-line parameters in bashrc/cshrc

- this provides a means to temporarily override the default settings
  and/or the prefs.{csh,sh} settings.

  bash:
      name=       -> unset name
      name=value  -> export name=value

  csh:
      name=       -> unsetenv name
      name=value  -> setenv name value

  eg,
      . <WM_PROJECT_DIR>/etc/bashrc WM_COMPILER=Gcc45 WM_MPLIB=
  to use gcc 4.5 and the default mplib

etc/bashrc

@@ -90,6 +90,22 @@ _foamSource()
 foamPrefs=`$WM_PROJECT_DIR/bin/foamEtcFile prefs.sh` && _foamSource $foamPrefs
 unset foamPrefs
 
+# Evaluate command-line parameters
+while [ $# -gt 0 ]
+do
+    case "$1" in
+    *=)
+        # name=       -> unset name
+        eval "unset ${1%=}"
+        ;;
+    *=*)
+        # name=value  -> export name=value
+        eval "export $1"
+        ;;
+    esac
+    shift
+done
+
 
 # Operating System/Platform
 # ~~~~~~~~~~~~~~~~~~~~~~~~~

etc/cshrc

@@ -78,6 +78,21 @@ if ( $status == 0 ) then
 endif
 unset foamPrefs
 
+# Evaluate command-line parameters
+while ( $#argv > 0 )
+    switch ($argv[1])
+    case *=:
+        # name=       -> unsetenv name
+        eval "unsetenv $argv[1]:s/=//"
+        breaksw
+    case *=*:
+        # name=value  -> setenv name value
+        eval "setenv $argv[1]:s/=/ /"
+        breaksw
+    endsw
+    shift
+end
+
 
 # Operating System/Platform
 # ~~~~~~~~~~~~~~~~~~~~~~~~~

etc/settings.csh

@@ -121,7 +121,10 @@ case OpenFOAM:
         set gccDir=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER_ARCH/$gcc_version
         set gmpDir=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER_ARCH/$gmp_version
         set mpfrDir=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER_ARCH/$mpfr_version
-        set mpcDir=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER_ARCH/$mpc_version
+        if ( $?mpc_version ) then
+            set mpcDir=$WM_THIRD_PARTY_DIR/platforms/$WM_ARCH$WM_COMPILER_ARCH/$mpc_version
+        endif
+
 
         # Check that the compiler directory can be found
         if ( ! -d "$gccDir" ) then