lib/arm: allow choosing adler32_neon() at runtime
lib/arm: allow choosing adler32_neon() at runtime

Now that we detect CPU features on ARM, allow the NEON implementation of
Adler-32 to be selected at runtime based on the presence of the NEON
feature.

ebiggers/libdeflate,ebiggers/libdeflate,ebiggers/libdeflate