Basic support for Android

This branch has two main goals:
- Replace the "underside" of the Android port with OpenGL ES2.
  Note that the rendering of games is still TinyGL.
  Main reason for this switchover is that OpenGL ES2 cannot be mixed with ES1.
- Add basic, but functional, touchscreen controls.
  Short summary:
  - Touching and holding the left side of the screen functions as a joystick.
  - Swiping the middle side allows fine control over arrow keys (eg. dialogues), tapping it sends an enter key.
  - Swiping the right side up/down sends pageup/pagedown. Swiping left/right form the right side allows further verbs like (I)nventory, (P)ickup, (U)se and (L)ook at.