win32: events stop processing when menubar is active

[tronical]

When a menu from the menubar is visible/open on Windows, the main event loops stops processing. To reproduce, apply the following patch to the winit.rs example:

diff --git a/examples/winit.rs b/examples/winit.rs
index 1911bae..9fba310 100644
--- a/examples/winit.rs
+++ b/examples/winit.rs
@@ -141,6 +141,10 @@ impl ApplicationHandler<AppEvent> for App {
                 self.use_window_pos = !self.use_window_pos;
             }

+            WindowEvent::RedrawRequested => {
+                eprintln!("redraw {:#?}", std::time::Instant::now());
+            }
+
             _ => {}
         }
     }
@@ -157,6 +161,15 @@ impl ApplicationHandler<AppEvent> for App {
             }
         }
     }
+
+    fn about_to_wait(&mut self, event_loop: &ActiveEventLoop) {
+        for (_, window) in &self.windows {
+            window.request_redraw();
+        }
+        event_loop.set_control_flow(winit::event_loop::ControlFlow::WaitUntil(
+            std::time::Instant::now() + std::time::Duration::from_millis(16),
+        ));
+    }
 }

 struct AppMenu {

Observe how every 16 ms the redraw message is printed, but that stops when a menu from the menubar is opened.