AES-NI and PCLMULQDQ support

[wqweto]

I recently had to tweak cifra to auto-detect AES-NI and PCLMULQDQ instruction set availability on host CPU and switch to faster AES-GCM implementation at run-time.

Do you care for a PR to boost minicrypto performance or prefer keeping cifra dependancy on stock repo version?

[kazuho]

Thank you for asking.

Generally speaking, I think we'd prefer optimizations getting upstreamed, rather than maintaining the changes ourselves.