CONFIG: address differences between shells

- suppress error messages that appear with zsh.
  According to unset(1p), 'unset -f' unsets a function.
  If the function was not previously defined, this is a no-op.
  This is similar for zsh, but there it emits a warning if the
  function was not previously defined.

- avoid 'local' in functions sources from etc/bashrc.
  ksh does not support this.

- use 'command' shell builtin instead of 'type'.
  Seems to be more consistent between shell flavours.

etc/config.csh/unset

@@ -167,8 +167,6 @@ if ( $?foamClean ) then
 endif
 
 
-unset cleaned foamClean foamOldDirs
-
 #------------------------------------------------------------------------------
 # Cleanup aliases
 
@@ -198,5 +196,9 @@ unalias wmRefresh
 unalias foamVersion
 unalias foamPV
 
+#------------------------------------------------------------------------------
+# Intermediate variables (do as last for a clean exit code)
+
+unset cleaned foamClean foamOldDirs
 
 #------------------------------------------------------------------------------