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/epoll.h

@@ -0,0 +1,49 @@
+#ifndef _SYS_EPOLL_H
+#define _SYS_EPOLL_H 1
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <stdint.h>
+#include <signal.h>
+
+union epoll_data
+{
+	void* ptr;
+	int fd;
+	uint32_t u32;
+	uint64_t u64;
+};
+typedef union epoll_data epoll_data_t;
+
+struct epoll_event
+{
+	uint32_t events;
+	epoll_data_t data;
+};
+
+#define EPOLL_CTL_ADD 0
+#define EPOLL_CTL_MOD 1
+#define EPOLL_CTL_DEL 2
+
+#define EPOLLIN      0x01
+#define EPOLLOUT     0x02
+#define EPOLLPRI     0x04
+#define EPOLLERR     0x08
+#define EPOLLHUP     0x10
+#define EPOLLET      0x20
+#define EPOLLONESHOT 0x40
+
+#define EPOLL_CLOEXEC 1
+
+int epoll_create(int size);
+int epoll_create1(int flags);
+int epoll_ctl(int epfd, int op, int fd, struct epoll_event* event);
+int epoll_wait(int epfd, struct epoll_event* events, int maxevents, int timeout);
+int epoll_pwait(int epfd, struct epoll_event* events, int maxevents, int timeout, const sigset_t* sigmask);
+int epoll_pwait2(int epfd, struct epoll_event* events, int maxevents, const struct timespec* timeout, const sigset_t* sigmask);
+
+__END_DECLS
+
+#endif

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
 {