Update xxhash to r37.
Use XXH64 on 64-bit systems.

I'm not able to reproduce any real performance difference, but I know
there are some games which do more hashing and it may help there.
Merge pull request #7028 from unknownbrackets/xxhash-update

Update xxHash to r37, including XXH64
jit: Fix partial invalidation of larger blocks.

Fixes #7031.
jit: Use the end just to be safe.

In case clearing near the end of a block.
Merge pull request #7032 from unknownbrackets/jit-minor

jit: Fix partial invalidation of larger blocks
Fix D3D NFSU crash #7030 in a cleaner way than #7033 :)
Add a non-SSE implementation of the QuickTexHash.

This way we can use it as a stable value for texture replacements.
Attempt to match the SSE2 version of the hash.

Not tested, don't currently have an ARM device.  May or may not have a
performance hit.
Fix reversed consts in hand-neon texhash.