ANDROID: Enable support for OpenGL ES2
ANDROID: Unpack library from lib/... instead of mylib
ANDROID: Switch renderer to GL ES2
ANDROID: Don't compress assets, skip asset header
GRAPHICS: Introduce Shader object
ANDROID: Add kVirtControls to OSystem_Android
ANDROID: Joystick movement and swipes
GRIM: Don't override fullscreen set by backend
ANDROID: Support swipe-based virtcontrols

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.
ANDROID: Move event types to separate file
ANDROID: Refactor touch controls to separate class
ANDROID: Access extra verbs by swiping from right
ANDROID: Always enable blending for touch controls.