py: Implement full func arg passing for native emitter.

This patch gets full function argument passing working with native
emitter.  Includes named args, keyword args, default args, var args
and var keyword args.  Fully Python compliant.

It reuses the bytecode mp_setup_code_state function to do all the hard
work.  This function is slightly adjusted to accommodate native calls,
and the native emitter is forced a bit to emit similar prelude and
code-info as bytecode.

py/asmthumb.c

@@ -106,6 +106,10 @@ STATIC byte *asm_thumb_get_cur_to_write_bytes(asm_thumb_t *as, int num_bytes_to_
     }
 }
 
+uint asm_thumb_get_code_pos(asm_thumb_t *as) {
+    return as->code_offset;
+}
+
 uint asm_thumb_get_code_size(asm_thumb_t *as) {
     return as->code_size;
 }