32-bit fast hash, tidy up murmur3 a bit

32-bit fast hash, tidy up murmur3 a bit

Nothing too surprising in the new 32-bit x86 hash.  It's about half speed of the 64-bit variant, just as you'd expect.

Using unaligned_load like the others makes the may_alias parts of murmur3 moot.  I've updated some of the terms in the murmur hash to read consistently with the others.

The existing hashes are the same speed and produce the same hashes.  In case this is not obvious, all three hash functions produce different hashes.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2251773002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review-Url: https://codereview.chromium.org/2251773002