Convert all CLUT entries ever loaded.

Some games reuse previously loaded bytes, like World Neverland.  We
displayed bad colors in these cases when we don't convert all the entries.

Technically, this means we're hashing less than used in these cases, but if
we hash more we will get lots of false cache misses.

Fixes #6752.
Merge pull request #6755 from unknownbrackets/clut-fix

Convert all CLUT entries ever loaded