Fixed assigning arguments to slots in the frame; also fixed a bug in bind...

But did that by switching away from using Lisp calling convention, because
that broke horribly. This is bad news and must be sorted out.

src/c/payloads/stack.h

@@ -37,7 +37,8 @@ struct stack_frame_payload {
     uint32_t depth;
 };
 
-struct pso_pointer make_frame( struct pso_pointer previous, ... );
+struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
+                               ... );
 
 struct pso_pointer destroy_stack_frame( struct pso_pointer fp,
                                         struct pso_pointer env );