Fix MSL_C / MSL_C++ / PowerPC_EABI_Support

The headers we imported were incorrect in a few aspects (std::cosf etc), and our modifications probably didn't make things better (e.g. a handful of game files are doing #include "__va_arg.h", some of our headers are/were clearly conflicting because we copied from multiple projects, ...).

Might be best to do throw away the files in this project, copy from TP, and then fix all the breakage in game code.