Fixed remaining xcode osx build errors

- system apis need to not require const references
- clang hates this when passing const values, as it probably should
- We now allow non-reference params, and treat them as const from the
  perspective of scripts, since the c++ side will pass by value
- Removed external opengl-4.3 include dir, which was busting the
  osx opengl include paths and breaking the renderer build big time
- Removed #include <GL/glcorearb.h> for all but win32, should
  investigate why we needed this include as I can't recall now
Fixed some additional xcode warnings, cleanup

- Removed "Source Files/Header Files" filters from xcode project
- Added -std=c11 flag to clang to supress a warning in the flex
  generated code
- Removed codegen_cpp type_str function as it was unused
- Added noinput and nounput options to flex spec, will test
  when back on windows, but should fix a couple of warnings
  about those functions being unused in the flex output.