Joystick range takes the dead-zone into account

This change scales the joystick range to include the deadzone. This allows the full -0x8000 to 0x8000 range to be read, with near-zero values right outside the deadzone (instead of jumping to 0x1000 when the deadzone is passed). Walking slowly and sneaking (like in Banjo Tooie, where you need to get past Sssslumber and the cave man), is now possible.
Forgot to add ASTICK_MAX, which I reference later

I used ASTICK_MAX in the calculations, but forgot to add its #define to the earlier commit.
Make a deadzone a bit smaller

A deadzone of 0x2000 (1/4th of the range) is sort of massive for any controller I've ever used. I made it 0x1000 (1/8th of the range).
Merge pull request #104 from vgf89/dead_zone_compensation

Dead zone compensation