Bugfix: Wrong start value for deferredFragShader.glsl.relevantSize
Cleanup.
Optimization: True zero checking for corners in deferredFragShader.glsl
Optimization: added lookup var idH for inverse dH in
deferredFragShader.glsl.
Optimization: Use of ceil() in place of floor()+1,
deferredFragShader.glsl.
Optimization: Pre-computed ceiling(texelXY) in deferredFragShader.glsl.