Use avx extensions

For traversing and dumping we already use SSE4.2 if available which makes a difference to the former brute force loop. Using AVX might further speed it up.

See: https://github.com/WojciechMula/sse4-strstr for lookup, maybe ffsll
https://en.wikipedia.org/wiki/Advanced_Vector_Extensions#CPUs_with_AVX-512

Note: Probably AVX512 is the more interesting one but requires a very recent CPU. 