core:sys/linux Add timerfd syscall wrappers

[salfel]

Needed those syscalls in one of my projects, so just added them as they were not present before.

Below is also a file to test the functionality of the syscall

package main

import "core:fmt"
import "core:os"
import "core:sys/linux"

main :: proc() {
	timer_fd, _ := linux.timerfd_create(.MONOTONIC, {.NONBLOCK})
	timer_spec := linux.ITimer_Spec {
		interval = {time_nsec = 500 * 1000 * 1000},
		value = {time_sec = 1},
	}
	linux.timerfd_settime(timer_fd, nil, &timer_spec, nil)
	pollfds := []linux.Poll_Fd{{fd = cast(linux.Fd)timer_fd, events = {.IN}}}

	for {
		if ret, err := linux.poll(pollfds, -1); err != nil || ret < 0 {
			if err == .EINTR {
				continue
			}

			fmt.eprintln("poll error:", err)
			break
		}
		if .IN in pollfds[0].revents {
			buf := [8]byte{}
			size, _ := os.read(cast(os.Handle)timer_fd, buf[:])

			fmt.println("received timer", transmute(u64)buf)
		}
	}
}