patch 7.4.1617

Problem:    When a JSON message is split it isn't decoded.
Solution:   Wait a short time for the rest of the message to arrive.

src/structs.h

@@ -1357,6 +1357,14 @@ typedef struct {
     jsonq_T	ch_json_head;	/* header for circular json read queue */
     int		ch_block_id;	/* ID that channel_read_json_block() is
 				   waiting for */
+    /* When ch_waiting is TRUE use ch_deadline to wait for incomplete message
+     * to be complete. */
+    int		ch_waiting;
+#ifdef WIN32
+    DWORD	ch_deadline;
+#else
+    struct timeval ch_deadline;
+#endif
 
     cbq_T	ch_cb_head;	/* dummy node for per-request callbacks */
     char_u	*ch_callback;	/* call when a msg is not handled */