Distorted Android

1) bugfix computing Gaussian BLUR kernel (for odd radii, the last offset was incorrectly computed)
2) introduce more advanced method of detecting BLUR halo (compute depths in a new way)

Roll back the recent MIPMAP work.

Preliminary support for MIPMAP levels of the postprocessing buffers. (doesn't work yet)

Merging blurred surfaces mostly ok now (blurred image still appears a bit shifted down for some reason)

Simplify shaders.

Make it more flexible; now it can run almost all apps on OpenGL 2.0 contexts; OpenGL 3.0 ( with GLSL 3.00) required for POSTPROCESSING.

Upgrade from GLSL 1.00 to GLSL 3.00 ES
Introduce separate BLUR1 and BLUR2 shaders, the second one marging (writing to gl_FragDepth still does not work)

Simplify BLUR shader.

Simplify drawRecursive

simplify blitPriv()