Kernel: Rewrite the whole input system

PS/2 code is now kind of messed up, but it works. Keyboards and mice are
now an abstract class that is automatically exposed to userspace. This
will make adding USB input much nicer.

kernel/include/kernel/FS/DevFS/FileSystem.h

@@ -20,8 +20,6 @@ namespace Kernel
 		void add_device(BAN::RefPtr<Device>);
 		void add_inode(BAN::StringView path, BAN::RefPtr<TmpInode>);
 
-		int get_next_input_device() const;
-
 		void initiate_sync(bool should_block);
 
 	private: