patch 7.4.1451
Problem:    Vim hangs when a channel has a callback but isn't referenced.
Solution:   Have channel_unref() only return TRUE when the channel was
            actually freed.
diff --git a/src/proto/channel.pro b/src/proto/channel.pro
index 8dc4ad4..5fd7f14 100644
--- a/src/proto/channel.pro
+++ b/src/proto/channel.pro
@@ -4,7 +4,7 @@
 void ch_log(channel_T *ch, char *msg);
 void ch_logs(channel_T *ch, char *msg, char *name);
 channel_T *add_channel(void);
-void channel_may_free(channel_T *channel);
+int channel_may_free(channel_T *channel);
 void channel_free(channel_T *channel);
 void channel_gui_register(channel_T *channel);
 void channel_gui_register_all(void);