Auto benchmark button for Features

[alandtse]

Given we have A/B testing as a feature, we could probably create an auto benchmark option for any feature. It would basically be a button that could record fps or frametime or whatever toggling the feature on and off.

1. Add Feature Disable/Enable functions.
2. Add stats measuring.
3. When "benchmark" button is pressed, turn on stats measuring and measure with feature on.
4. Enable A/B testing after calling the disable function. Measure.
5. Perform proper averaging; delay before measuring to avoid the recompilation time (or even detect if recompiling is done).
6. Maybe could force the camera to rotate during the test. Flatrim already does this if you're idle too.