#396 mouse input lag under X11

[Benoit Pierre]

When using a high polling rate mouse on Linux with X11, the mouse cursor lags under Adventure Game Studio. This is due to the fact that Allegro will only process up-to 5 X11 events at a time, and so mouse motion events will pile up and the mouse cursor will lag.

The attached patch remove this limitation of only processing 5 events or less at a time.