Centered Crosshair

Fixes the annoying bug where the center of the crosshair doesn't actually match the center of the screen.

Example (Red Cross = Screen Center):

Vanilla Minecraft	With the Mod

If the crosshair is an uneven number of pixels wide (e.g. 3), it will still be offcenter but just by half a pixel.

This also works with any crosshair-changing resource packs!