These are complex nodes, and it's conceivable they may end up constant
in some circumstances within node groups, so folding support is useful.
Reviewed By: brecht
Differential Revision: https://developer.blender.org/D2084
* Simplify default color values, where each component was the same.
* Initialize closures as Null Closure, rather than assigning an existing closure, gets overwritten anyways.
OSL noise() function is generating NaN's in certain cases, fix for that goes to our
OSL branch.
Also add missing minimum weight and max closure checks to OSL, forgot to add these
when fixing another bug.
* Moved kernel/osl/nodes to kernel/shaders
* Renamed standard attributes to use geom:, particle:, object: prefixes
* Update stdosl.h to properly reflect the closures we support
* Fix the wrong stdosl.h being used for building shaders
* Add geom:numpolyvertices, geom:trianglevertices, geom:polyvertices attributes
