Added check for AVX on boot

[hyperbx]

TODO:

• Localise the error message in locale.cpp.
• Test on unsupported hardware (if failing, compile main.cpp with no-avx flag).
• Test on platforms other than Windows.

[grantmulholland]

Might not work out if hedge-dev/XenonRecomp#22 gets merged?

[hyperbx]

Might not work out if hedge-dev/XenonRecomp#22 gets merged?

I've added compile-time checks for x86 now, os::host::IsCapableCPU() now returns true on other architectures. It'll be the responsibility of those implementing support for other architectures to determine which features are supported or not.

[hyperbx]

Tested on unsupported hardware, ran into an illegal instruction. The static initialisers are probably being emitted with AVX code, which would be a bit of a pain to maintain. Closing for now.