[wayland] Pass X11 events through the native event filters

E.g. KSelectionOwner installs a native event filter and listens for
xcb events. Without that the KSelectionOwner::claim never succeeds and
for other X11 applications it will look like Compositing is not
supported.

main_wayland.cpp

@@ -184,6 +184,11 @@ void ApplicationWayland::continueStartupWithX()
     auto processXcbEvents = [this, c] {
         while (auto event = xcb_poll_for_event(c)) {
             updateX11Time(event);
+            long result = 0;
+            if (QThread::currentThread()->eventDispatcher()->filterNativeEvent(QByteArrayLiteral("xcb_generic_event_t"), event, &result)) {
+                free(event);
+                continue;
+            }
             if (Workspace::self()) {
                 Workspace::self()->workspaceEvent(event);
             }