Speed up ISO reading for the gameinfocache

On Windows, new is the biggest consumer (I turned off caching to see what was up.)  Seems like a likely story for mobile.

After that was inflate and fread.  The best way to optimize that would be to fast-path a single directory lookup by path, so I did that.

Now fread is the top consumer by far (70%) and the next is CreateFile (13.8%.)  Most of the read is actually in the CISO constructor reading the index I presume.

-[Unknown]