Detach framebuffers when texcache match fails

Otherwise, `entry->framebuffer` stays set, even if another framebuffer (or even the same one) might be valid.  This allows it to reset the cache entry settings.

Also, I noticed a small bug in DrawPixels(), but it's probably super unlikely to ever be hit.

This might help the FF Type-0 issue, but I am not seeing it currently... Tactics Ogre, Valkyrie Profile, and Mana Khemia (which are picky about these renders) seem to be no worse.  @solarmystic and @raven02, I could use some help testing this with other games that are temperamental in this area.

-[Unknown]