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:

userspace/libraries/LibC/include/sys/syscall.h

@@ -98,6 +98,9 @@ __BEGIN_DECLS
 	O(SYS_PTHREAD_EXIT,		pthread_exit)	\
 	O(SYS_PTHREAD_JOIN,		pthread_join)	\
 	O(SYS_PTHREAD_SELF,		pthread_self)	\
+	O(SYS_EPOLL_CREATE1,	epoll_create1)	\
+	O(SYS_EPOLL_CTL,		epoll_ctl)		\
+	O(SYS_EPOLL_PWAIT2,		epoll_pwait2)	\
 
 enum Syscall
 {