cpufeatures: additional AVX-512 features

[tarcieri]

862 added initial support for AVX-512, however the following features are still unsupported:

• [ ] avx512vbmi
• [ ] avx512vbmi2
• [x] avx512vpopcntdq
• [ ] avx512vnni
• [x] avx512bitalg
• [ ] avx512bf16
• [ ] avx512vp2intersect

These use different CPUID registers than the others (e.g. ecx)

Edit: updated after #1035

[brxken128]

This comment details my findings in regards to avx512vbmi(2).

I'd still double check first, however I'm more than happy to run any tests that'd help validate things.

Sadly my CPU doesn't have support for any of the others.