Use $(SHELL) and $(KORNSHELL) for shell scripts

Introduce KORNSHELL make variable to point
to the implementation of the Korn Shell.

Use $(SHELL) or $(KORNSHELL) explicitly for
make programs that do not automatically call
shell scripts from the current directory.

cde/programs/localized/templates/header2.tmpl

@@ -87,7 +87,7 @@ includes::								@@\
 	$(MAKEMESSCAT) $(GENCATFLAGS) $@ $(LANG)
 #endif
 
-MAKEMESSCAT = $(CDESRC)/localized/util/makeMessCat
-SYM2NUM_CMD = $(CDESRC)/dtprintinfo/sym2num
+MAKEMESSCAT = $(KORNSHELL) $(CDESRC)/localized/util/makeMessCat
+SYM2NUM_CMD = $(SHELL) $(CDESRC)/dtprintinfo/sym2num
 
 MsgCatRule()