Add glfwWaitEventsTimeout

This function will put the calling thread to sleep until an event
arrives or until the specified timeout has elapsed.

src/win32_window.c

@@ -1142,6 +1142,13 @@ void _glfwPlatformWaitEvents(void)
     _glfwPlatformPollEvents();
 }
 
+void _glfwPlatformWaitEventsTimeout(double timeout)
+{
+    MsgWaitForMultipleObjects(0, NULL, FALSE, (DWORD) (timeout * 1e3), QS_ALLEVENTS);
+
+    _glfwPlatformPollEvents();
+}
+
 void _glfwPlatformPostEmptyEvent(void)
 {
     _GLFWwindow* window = _glfw.windowListHead;