Keep track of x/y offset for render-to-tex.

Fixes intro in Valkyrie Profile now that we're wrapping correctly.
Ignore needShaderTexClamp when not texmapping.
Use an extra shader id bit to skip offsetting.

Since the vast majority of the time it will be 0.
Merge pull request #6259 from unknownbrackets/fbtex-offset

Apply byte offset when using rendered textures