fixed minor coding and styling issues.
Merge pull request #305 from est77/OSL_merge

OSL merge #10
fixed minor styling issues.
fixed the definition of OVERRIDE with gcc.
fixed coding and styling issues.
renderer::OSLBSDF::bsdf_to_closure_id() now returns a reference.
refactoring.
Added missing Closure -> BSDF conversions, bug fixes and formatting fixes.