oslc adjustment for newer OSX releases: can't count on /usr/bin/cpp-4.2, only use it if present, otherwise fall back on /usr/bin/cpp. While I'm in there, change several references to boost::filesystem::exists to OIIO::Filesystem::exists, which wraps it to catch exceptions.
oslc adjustment for newer OSX releases: can't count on /usr/bin/cpp-4.2, only use it if present,
otherwise fall back on /usr/bin/cpp.
While I'm in there, change several references to boost::filesystem::exists to
OIIO::Filesystem::exists, which wraps it to catch exceptions.

sjparker/OpenShadingLanguage,mcanthony/OpenShadingLanguage,lgritz/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,imageworks/OpenShadingLanguage,imageworks/OpenShadingLanguage,rlmh/OpenShadingLanguage,aconty/OpenShadingLanguage,aconty/OpenShadingLanguage,lgritz/OpenShadingLanguage,sjparker/OpenShadingLanguage,aconty/OpenShadingLanguage,Anteru/OpenShadingLanguage,gzorin/OpenShadingLanguage,lgritz/OpenShadingLanguage,Anteru/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,svenstaro/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,rlmh/OpenShadingLanguage,gzorin/OpenShadingLanguage,brechtvl/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,imageworks/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,gzorin/OpenShadingLanguage,mcanthony/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,rlmh/OpenShadingLanguage,Anteru/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,brechtvl/OpenShadingLanguage,lgritz/OpenShadingLanguage,gzorin/OpenShadingLanguage,aconty/OpenShadingLanguage,brechtvl/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,Anteru/OpenShadingLanguage,imageworks/OpenShadingLanguage,juvenal/OpenShadingLanguage,svenstaro/OpenShadingLanguage,sjparker/OpenShadingLanguage,lgritz/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,svenstaro/OpenShadingLanguage,imageworks/OpenShadingLanguage,rlmh/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,juvenal/OpenShadingLanguage,aconty/OpenShadingLanguage,juvenal/OpenShadingLanguage,gzorin/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,brechtvl/OpenShadingLanguage,brechtvl/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,sjparker/OpenShadingLanguage,svenstaro/OpenShadingLanguage,mcanthony/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,juvenal/OpenShadingLanguage,mcanthony/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage