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/config/cf/Imake.tmpl

@@ -180,6 +180,9 @@ XCOMM the platform-specific parameters - edit site.def to change
 #ifndef BourneShell			/* to force shell in makefile */
 #define BourneShell		/bin/sh
 #endif
+#ifndef KornShell
+#define KornShell		/bin/ksh
+#endif
 #ifndef ConstructMFLAGS
 #if SystemV
 #define ConstructMFLAGS		YES	/* build MFLAGS from MAKEFLAGS */
@@ -889,6 +892,7 @@ XCOMM the platform-specific parameters - edit site.def to change
 
           PATHSEP = PathSeparator
             SHELL = BourneShell
+        KORNSHELL = KornShell
 
               TOP = TOPDIR
       CURRENT_DIR = CURDIR