ANDROID: Rewrite to make use of OpenGLGraphicsManager #1695
Previously, the Android backend used its own custom OpenGL code for rendering. This PR replaces that with the common OpenGL rendering code.
This is not finished. It's just about usable, but there are still several major caveats regarding this PR:
However, I'm currently stuck regarding how to fix these issues, so I've opened this PR anyway in the hope that someone else might be able to help with this.