BGE: Fix for [#33053] "2.6x Joystick Sensor Event: Axis fails to fire at full tilt" reported by Auuman Anubis (auuman_anubis).

The problem was that SCA_Joystick::pAxisTest() was using shorts, and tried to store abs(MIN_SHRT) in a short. However, on most systems MIN_SHRT == -32768 and MAX_SHRT == 32767. This means that abs(MIN_SHRT) > MAX_SHRT, and thus the short would overflow.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53617 954f8c5b-7b00-dc11-b283-0030488c597c