os: create epoll wrapper (#10404)

vlib/os/notify/notify.v

@@ -0,0 +1,35 @@
+module notify
+
+import time
+
+// Backends should provide a `new() ?FdNotifier` function
+pub interface FdNotifier {
+	add(fd int, events FdEventType, conf ...FdConfigFlags) ?
+	modify(fd int, events FdEventType, conf ...FdConfigFlags) ?
+	remove(fd int) ?
+	wait(timeout time.Duration) []FdEvent
+	close() ?
+}
+
+pub interface FdEvent {
+	fd int
+	kind FdEventType
+}
+
+[flag]
+pub enum FdEventType {
+	read
+	write
+	peer_hangup
+	exception
+	error
+	hangup
+}
+
+[flag]
+pub enum FdConfigFlags {
+	edge_trigger
+	one_shot
+	wake_up
+	exclusive
+}