ENH: more tuning parameters for user environment

- FOAM_CONFIG_NOUSER
  Suppress use of user/group configuration files.
  This is useful when packaging for a central installation.

- allow additional user tuning of compiler settings.
  Per-compiler overrides in "compiler-$WM_COMPILER" files

etc/config.sh/functions

@@ -16,7 +16,7 @@
 # Description
 #     Shell functions and variables used when sourcing the OpenFOAM environment
 #
-#     Some functionality is shadowed in bin/tools/lib-dir
+#     Some functionality mirrored by bin/tools/lib-dir
 #
 #------------------------------------------------------------------------------
 
@@ -33,11 +33,27 @@ then
     # Cleaning environment variables
     _foamClean()
     {
-         local var=$1
+         foamVar_name=$1
          shift
-         eval $($WM_PROJECT_DIR/bin/foamCleanPath -sh-env=$var "$@")
+         eval $($WM_PROJECT_DIR/bin/foamCleanPath -sh-env=$foamVar_name "$@")
+         unset foamVar_name
     }
 
+    # Source an etc file, possibly with some verbosity
+    # - use eval to avoid intermediate variables (ksh doesn't have 'local')
+    if [ "$FOAM_VERBOSE" -a "$PS1" ]
+    then
+        _foamEtc()
+        {
+            eval "$($WM_PROJECT_DIR/bin/foamEtcFile -sh-verbose ${FOAM_CONFIG_NOUSER:+-mode=o} $@)";
+        }
+    else
+        _foamEtc()
+        {
+            eval "$($WM_PROJECT_DIR/bin/foamEtcFile -sh ${FOAM_CONFIG_NOUSER:+-mode=o} $@)";
+        }
+    fi
+
     # Prepend PATH
     _foamAddPath()
     {
@@ -133,15 +149,6 @@ then
     fi
 
 
-    # Source an etc file, possibly with some verbosity
-    # - use eval to avoid intermediate variables (ksh doesn't have 'local')
-    if [ "$FOAM_VERBOSE" -a "$PS1" ]
-    then
-        _foamEtc(){ eval "$($WM_PROJECT_DIR/bin/foamEtcFile -sh-verbose $@)"; }
-    else
-        _foamEtc(){ eval "$($WM_PROJECT_DIR/bin/foamEtcFile -sh $@)"; }
-    fi
-
     # Evaluate command-line parameters
     _foamEval()
     {