Multiplayer, and some other stuff

Hello, hello. I've added a cluster of management stuff, so there's now support for controllers, multiplayer, and a few other things. 

I also did a bunch of optimization stuff (along with recompiling with the correct compiler that's several times faster by default, oops). So the game should be speedy and work proper now, I can't guarantee leaving the game will work correctly/not crash every time though. There's still probably some little edge cases I missed where the game doesn't know what to do with a player that no longer exists but I checked most of what I could think of. 

Some little gameplay things include knockback on rockets and some new item sprites and tweaks. 

Either way, enjoy if you wish. It will keep updating for the foreseeable future.