Support render-to-self on GLES2.
Don't use shader blending without buffers.

Ugh, making ComputeFragmentShaderID() slower again...
Support block transfer uploads in non-buffered.
Allow a memcpy upload in non-buffered rendering.
Merge pull request #6191 from unknownbrackets/gpu-minor

Allow uploads to framebuffers in non-buffered, disable shader blending