Distorted Android

Finally properly fix the flashing on ARM Mali T880 GPU.

The flashing is caused by a 'full pipeline flush' (see DarkPhoton, https://www.opengl.org/discussion_boards/showthread.php/200754-Flashes-on-ARM-Mali?p=1291679&viewfull=1#post1291679 ). In order to combat it, first introduce the possibility that a single DistortedOutputSurface is backed up by more than one FBO. Then make DistortedScreen be derived from DistortedFramebuffer (which itself is derived from DistortedOutputSurface) and make it contain 3 FBOs, render to them in a circular queue fashion, and blit from a given FBO to the system FBO. The 'more than 1 intermediate FBO' queue prevents the pipeline flush....

Minor.

Port all the 'non-controversial' changes from order-independent-transparency branch.

Fixes ported from the 'OIT' branch:

- remove counting of transparent pixels
- various fixes for the Mali GPU

Minor.

Disable blending during postprocessing.

Fix for bug #28: looks of the borders of a blurred object depend on if the object is the first in the postprocessing bucket.

Postprocessing buffers mBuffer[] are now shared among all postprocessing operations. This saves a lot of memory, but also means that when doing each particular postprocessing, the textures backing up the mBuffer might be too large. We need to fix two things here: when outputting to those too large textures, we need to adjust the Viewport, and when binding those too large textures as input - we need to adjust the TexCoords to compensate....

Improve the 'PostprocessTree' app. Shows bugs in postprocessing.

Simplify postprocessing buffers.