This kills the funky GL logging stubs, which unnecessarily
complicates the build process (think future cmake).
As for logging GL calls: Use apitrace for that
https://github.com/apitrace/apitrace
Thread return types are different between platforms, and its
probably not a good idea to return something of a different size,
cast the callback and expect it to not crash.
Let scons link directly in the build folder.
Multiple archs can coexist next to each other.
New scons variable "X86" to cross compile x86 binaries on x86_64.
