add lwc1 lwc2 swc1 swc2 opcodes
Merge pull request #7014 from BlackDogDog/master

add lwc1 lwc2 swc1 swc2 opcodes
Some very minor optimizations. Remove little-used stat counter.
Use unordered_map where it makes sense. Very tiny speed boost?

Also some microoptimizations.
Merge https://github.com/hrydgard/ppsspp