Fix missing Detection for AVX OS Support #4325
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A Fix for Issue #4323, where now in addition to the CPU Capabilities, the OS Support is also queried when checking for AVX/AVX2/AVX512 availability.
This is done by an additional check to the XCR_XFEATURE Register using the xgetbv instruction. Since this is not present on some older CPU's, we first need to check for it's availability with CPUID EAX=1 for bits 26 and 27 in ECX.
Tested on my System with an i7 7800X and Win8.1 (with support for AVX/AVX2 but not for AVX512), where avx/avx2 are still enabled, but avx-512 is now correctly disabled. Might require further testing on machines where AVX512 is confirmed to work as well as on linux.