So a lot of alterations had to be done to make this not worse and
so far, it's not really better, either. I had to force inlining for
the adler routine, I had to remove the x4 load instruction otherwise
pipelining stalled, and I had to use restrict pointers with a copy
idiom for GCC to inline a copy routine for the tail.
Still, we see a small benefit in benchmarks, particularly when done
with size of our window or larger. There's also an added benefit that
this will fix#1824.
It's unclear if raspberry pi OS's shipped GCC doesn't properly detect
ACLE or not (/proc/cpuinfo claims to support AES), but in any case, the
preprocessor macro for that flag is not defined with -march=native on a
raspberry pi 5. Unfortunately that means when built "WITH_NATIVE", we do
not get a fast CRC function. The CRC32 preprocessor macro _IS_ defined,
and the auto detection when built without NATIVE support does properly
get dispatched to. Since we only need the scalar CRC32 and not the polynomial
stuff anyhow, let's make it be an || condition and not a && one.
