GTK3, system SDL2 (pkg-config), Linux link libraries, linker groups,
and _GLIBCXX_DEBUG were in the generic non-MSVC branch, breaking
cmake configure on non-Linux POSIX platforms.
Based entirely off existing xbyak x86 implementation and available
tests. Still needs a lot of optimization and testing on non-Windows
platforms.
So far passes all tests and boots at least some games on Windows.
version.h is now found via CMAKE_BINARY_DIR on the include path instead
of a hardcoded "build/version.h" path. This allows out-of-tree and
multi-config builds to each generate and find their own version header
without colliding.
