Rewrite identd

- Use gio (which is cross platform)
- Properly support multiple users
- Allow configuring port
- Allow other plugins overriding

src/common/hexchat.h

@@ -263,6 +263,7 @@ struct hexchatprefs
 	int hex_gui_win_state;
 	int hex_gui_win_top;
 	int hex_gui_win_width;
+	int hex_identd_port;
 	int hex_input_balloon_time;
 	int hex_irc_ban_type;
 	int hex_irc_join_delay;