Distorted Android

First try to convert the Stencil app to a dual (directly to Screen / through intermediate Framebuffer) mode.
Doesn't work yet ( API is inconvenient / plain wrong )

Add possibility to create FBOs with combined DEPTH/STENCIL.

Simplify setting up DistortedScreen.

1. Correct some bugs in DistortedRenderState
2. Thus make the Stencil App work
3. New icon for it

Progress with Stencil App; should be working now AFAIK but doesn't.

Beginnings of Stencil App.

Some corrections so that most apps still work on the Android emulator (OpenGL ES 2.0-based)

Merge branch 'transform-feedback'

Use Transform Feedback to (optionally) display the Normal vectors.

Minor bugfix.