v5.1.2

I didn't really mean to push this build, but it seems 5.1.1 was built wrong for some reason, and (still can't see why), it causes issues with local play in games such as Smash Bros and New Super Mario Bros 2.
The same code worked fine from a different build.
So here's a quick rebuild. The only changes from 5.1.1 were a general code cleanup and a FatFs update, nothing too fancy.