Fixed building on OSX 10.5 and newer

Hello.

This patch fixes building OpenCollada on mac OSX-10.5 and newer. I can not test it by myself and i rely on what the OSX Maintainer from Blender (Jens Verwiebe) reported to me.

Jens also asked following questions:

1. why are the buildsystems so different in available and needed options ? for example (non-)native pcre
2. whats the issue in using tr1/unordered vs. (std::) unordered
3. perhaps you should check llvm/gcc compiling in that area missing some types that clang( c++11 ) does not need.

Thanks,
Gaia