Misc. improvements / fixes

- Fixed gcc compile error.
- Compatibility with latest OIIO / OSL releases (SIMD optimizations).
- Added OSL texture test scene.
- Fixed OSL test scenes sphere uv coordinates.
- Started de-duplicating things in test scenes.
- Formatting changes.

I usually use development versions of both OIIO and OSL.
The problem in this particular case is the API changes.
The OIIO / OSL SIMD changes does not compile yet with some gcc versions,
but when it does, we can upgrade and get approx 2X faster texture lookups.