Kernel/LibC: Implement basic epoll

This implementation is on top of inodes instead of fds as linux does it.
If I start finding ports/software that relies on epoll allowing
duplicate inodes, I will do what linux does.

I'm probably missing multiple epoll_notify's which may cause hangs but
the system seems to work fine :dd:

kernel/include/kernel/Networking/Loopback.h

@@ -30,6 +30,7 @@ namespace Kernel
 		bool can_read_impl() const override { return false; }
 		bool can_write_impl() const override { return false; }
 		bool has_error_impl() const override { return false; }
+		bool has_hangup_impl() const override { return false; }
 
 	private:
 		SpinLock m_buffer_lock;