Fix compile warnings in CCEffectsTest - Comment out unused shaders

But keep the the commented out code since they can be used to check the performance of
different effects.
CCEffectNode - Remove out of date comments. No functional change.
Fix CCEffectGlow

Instead of the renderer directly setting the render pass uniforms, give the previous
pass's render target to the current pass's begin block and let the pass handle it how
it likes.