Closes #18. Change to char32_t everywhere; builds fine, behaviour as before.

src/c/payloads/stack.c

@@ -33,6 +33,7 @@
  */
 struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
                                ... ) {
+	// todo: issue #21: must have stack frame passed in.
     va_list args;
     va_start( args, previous );