Texture cache pointer walking

Just in some hot areas I found, which should be endian-safe.

This improved the perf by at least 2-3% in Popolocrois (which uses a lot of textures and does some heavy invalidation.)  Maybe more.

Note: the under-estimating proved to make the has not invalidate when it used to so I doubled it, which seemed like the same factor maybe it was underestimating by...

-[Unknown]