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/dtprintinfo/Imakefile

@@ -68,7 +68,7 @@ DEFINES = -D_TOOLTALK
 #endif
 
 /* special processing for message files */
-SYM2NUM_CMD = ./sym2num
+SYM2NUM_CMD = $(SHELL) sym2num
 
 SRCS = DtPrintinfo.C
 OBJS = libUI/BaseUI.o objects/BaseObj.o DtPrintinfo.o