ficl: instead of pad, emit can use local variable

Pad in forth is used as "scratchpad" and internal implementations
should not use it. Ficl does not really follow this rule and this can fire back.
emit has no need to use pad, we can use local variable instead.

stand/ficl/words.c

@@ -1015,7 +1015,7 @@ static void twoSwap(FICL_VM *pVM)
 
 static void emit(FICL_VM *pVM)
 {
-    char *cp = pVM->pad;
+    char cp[2];
     int i;
 
 #if FICL_ROBUST > 1