5218 posix definition of NULL
correct unistd.h and iso/stddef_iso.h
update gate source affected

@@ -70,11 +70,11 @@
                 return(FAIL);
         gsig=signal(SIGALRM, galarm);
         if (Debug > 4)
                 pkdebug = 1;
         Pk = pkopen(Ifn, Ofn);
-        if ((int) Pk == NULL)
+        if ( Pk == NULL)
                 return(FAIL);
         return(0);
 }
 
 int