Log Message:
Update xmess to 0.81.1.

Changes since 0.80.1nb1:
- Everything from MAME 0.81 (http://x.mame.net/changes-mame.html) and
   MESS 0.81 (http://x.mame.net/changes-mess.html).
- Fixed a problem with the lightgun offscreen reloading that caused a
   random shot every fourth or fifth shot.  (Joe Inkenbrandt)