irc: fix display of status privmsg/notice, add missing tags in messages (issue #139)

The status PRIVMSG and NOTICE are now displayed the same way for outgoing and
received messages:

Msg(alice) -> @#test: message for ops
Notice(alice) -> @#test: notice for ops

And any message like this is displayed with these tags if the nick is self
nick (case of a bouncer or if capability "echo-message" is enabled):
"self_msg", "notify_none", "no_highlight".

src/plugins/irc/irc-input.h

@@ -23,7 +23,10 @@
 struct t_gui_buffer;
 
 extern void irc_input_user_message_display (struct t_gui_buffer *buffer,
-                                            int action, const char *text);
+                                            int action, int notice,
+                                            const char *target,
+                                            int target_is_channel,
+                                            const char *text);
 extern int irc_input_data_cb (const void *pointer, void *data,
                               struct t_gui_buffer *buffer,
                               const char *input_data);