input.cxx allocates memory for js->getNumAxes() axes and for jsCaps.wNumButtons
or MAX_JOYSTICK_BUTTONS buttons per joystick. But it doesn't check if some
xml config defines bindings for more axes/buttons, in which case it writes
to unallocated memory and causes crashes. This is a real world example:
sidewinder-force-feed-pro.xml defines 7 axes, but only newer versions of
this js do actually have that many. Older ones (-> gameport) don't. The patch
drops unused and unusable bindings.