Restructure monitor enumeration

This way is both kinder on event-based enumeration and less work to
unwind allocations for when properly implementing GLFW_OUT_OF_MEMORY.

src/x11_window.c

@@ -910,7 +910,7 @@ static void processEvent(XEvent *event)
         if (event->type == _glfw.x11.randr.eventBase + RRNotify)
         {
             XRRUpdateConfiguration(event);
-            _glfwInputMonitorChange();
+            _glfwPollMonitorsX11();
             return;
         }
     }