AMD R9 fix and added command-line options.

The fix for driver crashes on AMD R9 GPUs (and other models) has now been pushed to the default branch. Default and 'future' are currently the same now. If you don't like big patches, you can get off 'future' and back onto default, because the next patch on 'future' is likely to be another 1GB patch coming on Monday or Tuesday or so.

Here again are the changes:

We changed the depth format for shadow maps from D16 to D24, which seems to avoid a bug in the R9 drivers.

We also added some menu features people are asking for:

Added Invert X Axis to the options menu. Added FOV slider to the options menu. Added gamepad sensitivity to the options menu (if gamepad is plugged in).