Contribution: SSE2 fallbacks for NEON (arm Cortex-A8+ including all RaspberryPIs), SSE, MMX, pure source

[mr-c]

Hello, would this project be interested in a PR that adds support for all non-SSE2 systems using the https://github.com/nemequ/simde header-only library?

The PR would look something like the experiment I made at https://salsa.debian.org/med-team/libssw/blob/simde/debian/patches/simde.patch