Finish implementing GPU-side image transformation routines for OGL

[kd-11]

More of a note-to-self.
Some Z-buffer transformations cannot be done natively using the GL pipeline. Currently these are handled CPU-side when doing readback as we have to support old GPUs with this backend. Some operations such as typeless casts have to be done exclusively GPU-side; investigate a clean way of doing these operations without complex shader support.

Tasks:

• D24X8_UINT upload and download routines.
• D24X8_UINT typeless conversion.
• D24X8_FLOAT upload and download routines.
• D24X8_FLOAT typeless conversion.
• Image deswizzle routines.
• Image swizzle routines.

[kd-11]

First 4 items already implemented. The remaining points will be addressed during performance optimizations as they are not needed for correct rendering.

[Darkhost1999]

Isn't at least Image deswizzle routines completed in OGL bring up?

[kd-11]

You're right, I forgot to update.