[AD] Allegro linux joystick patch

[Peter Wang <tjaden@xxxxxxxxxx>]

Remember the problem of lagging joystick input on linux, and we weren't 
sure whether to read more than one event at a time?  The kernel doc 
(joystick-api.txt) says "You should read all events on the queue (that 
is, until you get a -1)."  Therefore the issue is decided.  I committed 
a patch to that effect.

Greg Lee should be credited for bringing this up, although I didn't use 
his patch.

Peter