Add Windows support for AVX/AVX-512 detection in cmake.

This issue covers two items:

Currently, the flags proc_supports_avx and proc_supports_avx512 are set only in UNIX. We need support for Windows in check_avx_processor_and_compiler_support and check_avx512_processor_and_compiler_support.
unit_test covering AVX/AVX-512 related code is UNIX specific as well. For example it is using UNIX specific compiler options. Also needs support for Windows.