Update to libgdx 1.0 API, remove gl10, fix RoboVM backend

Removed gl10 as that is removed in upstream libgdx, going gl20 and gl30 only. Fixed RoboVM backend to work with latest RoboVM and libgdx.

This is a rather invasive change - I tested it on my relatively simple platformer and everything works on desktop, android, and ios. Something that exercises the more subtle details of gl10/gl20 should probably also be taken for a test run.

RoboVM example apps needs to be tweaked to use this new API. That should be really easy though.