dix: Don't use short as bool

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>
Reviewed-by: Jamey Sharp <jamey@minilop.net>
Reviewed-by: Simon Thum <simon.thum@gmx.de>

dix/ptrveloc.c

@@ -714,7 +714,7 @@ ApplySofteningAndConstantDeceleration(
         int dy,
         float* fdx,
         float* fdy,
-        short do_soften)
+        BOOL do_soften)
 {
     if (do_soften && vel->use_softening) {
         *fdx = ApplySimpleSoftening(vel->last_dx, dx);