Cocoa: Fix window rect on leaving video mode

Fixes #748.

src/cocoa_window.m

@@ -1310,6 +1310,10 @@ void _glfwPlatformSetWindowMonitor(_GLFWwindow* window,
 
     _glfwInputWindowMonitorChange(window, monitor);
 
+    // HACK: Allow the state cached in Cocoa to catch up to reality
+    // TODO: Solve this in a less terrible way
+    _glfwPlatformPollEvents();
+
     const NSUInteger styleMask = getStyleMask(window);
     [window->ns.object setStyleMask:styleMask];
     [window->ns.object makeFirstResponder:window->ns.view];