Add a NEON version of the tex hash.

I'm not actually sure it's faster or slower (don't have a good way to compare, and performance on my mobile devices seems very uneven), but it uses roughly the same algorithm as SSE so it should be stronger than the current.

Would be curious if anyone can see performance improvements or hits with this.  It shouldn't really affect desktop, though.

Not added to Qt/cmake for now, just Android.

-[Unknown]