Test + fix for epoll and kqueue selector modules to properly unregister

event handles that have the key type "User"

lib/pure/ioselects/ioselectors_epoll.nim

@@ -197,7 +197,7 @@ proc unregister*[T](s: Selector[T], fd: int|SocketHandle) =
            "Descriptor $# is not registered in the selector!" % $fdi)
   if pkey.events != {}:
     when not defined(android):
-      if pkey.events * {Event.Read, Event.Write} != {}:
+      if pkey.events * {Event.Read, Event.Write, Event.User} != {}:
         var epv = EpollEvent()
         # TODO: Refactor all these EPOLL_CTL_DEL + dec(s.count) into a proc.
         if epoll_ctl(s.epollFD, EPOLL_CTL_DEL, fdi.cint, addr epv) != 0:

lib/pure/ioselects/ioselectors_kqueue.nim

@@ -375,7 +375,7 @@ proc unregister*[T](s: Selector[T], fd: int|SocketHandle) =
            "Descriptor [" & $fdi & "] is not registered in the queue!")
 
   if pkey.events != {}:
-    if pkey.events * {Event.Read, Event.Write} != {}:
+    if pkey.events * {Event.Read, Event.Write, Event.User} != {}:
       if Event.Read in pkey.events:
         modifyKQueue(s, uint(fdi), EVFILT_READ, EV_DELETE, 0, 0, nil)
         dec(s.count)

tests/async/testmanyasyncevents.nim

@@ -0,0 +1,23 @@
+discard """
+output: '''
+hasPendingOperations: false
+triggerCount: 512 
+'''
+"""
+
+import asyncDispatch
+
+var triggerCount = 0
+var evs = newSeq[AsyncEvent]()
+
+for i in 0 ..< 512: # has to be lower than the typical physical fd limit
+  var ev = newAsyncEvent()
+  evs.add(ev)
+  addEvent(ev, proc(fd: AsyncFD): bool {.gcsafe,closure.} = triggerCount += 1; true)
+
+for ev in evs:
+  ev.trigger()
+
+drain()
+echo "hasPendingOperations: ", hasPendingOperations()
+echo "triggerCount: ", triggerCount