patch 7.4.1166

Problem:    Can't encode a Funcref into JSON.  jsonencode() doesn't handle the
            same list or dict twice properly.  (Nikolay Pavlov)
Solution:   Give an error.  Reset copyID when the list or dict is finished.

src/proto/json.pro

@@ -1,5 +1,4 @@
 /* json.c */
 char_u *json_encode(typval_T *val);
-void json_encode_item(garray_T *gap, typval_T *val, int copyID);
 void json_decode(js_read_T *reader, typval_T *res);
 /* vim: set ft=c : */