Fix Texture3D parameters failing with "invalid dimensionality 1"

[wlewNV]

Fixes #655

TextureMarshall was not overriding resolve_dimensionality(), causing the default implementation to incorrectly calculate call_dimensionality=1 for textures passed as function arguments.

Added resolve_dimensionality() to TextureMarshall that returns:

• 0 when target type is a texture (broadcast as-is)
• texture_dims for per-pixel operations

[ccummingsNV]

Code looks good. If you have time to modify the texture tests to use none-square textures and none-zero coordinates that'd be great - generally good practice with graphics unit tests.

Approved either way though!

[ccummingsNV]

I'll deploy this if the merged version passes.