Add unreal_server_compat module which rewrites named extbans in

server to server traffic to be letter extbans.
Yeah this is a tad ugly, but the alternative was worse, see
header of the file for the full story.

Module is loaded by default (obviously).

Still to do: only do this for non-U6 servers (add some PROTOCTL)

And probably alter clean_ban_mask because I don't like the
magic on NULL client at the moment.

include/modules.h

@@ -375,6 +375,7 @@ typedef struct {
 	int what;		/**< MODE_ADD or MODE_DEL (for is_ok) */
 	int what2;		/**< EXBTYPE_BAN or EXBTYPE_EXCEPT (for is_ok) */
 	int is_ok_checktype;	/**< One of EXBCHK_* (for is_ok) */
+	int write_letter_bans;	/**< If set to 1 then we will always use letter extbans */
 } BanContext;
 
 typedef struct Extban Extban;