x86-64 doesn't require 3DNow as the README claims

[fuel-pcbox]

No Intel CPU has ever supported 3DNow instructions, and 3DNow isn't required by the x86-64 specifications, but the README claims it is for some reason.

[iximeow]

yeah, that's outright wrong. i'm not sure why i wrote that. 3dnow is accepted by the decoders by default though, even though those instructions presumably #UD on real hardware from the last decade and a half. thank you for filing the issue.

incidentally that means all the helpers to configure decoders for specific microarchitectures are also wrong (since they build on InstDecoder::minimal() and that itself is wrong). so, i'll fix that up at some point this week..