Windows: Fix shutdown order (stop the main thread before the window gets destroyed)

Windows/MainWindow.cpp

@@ -968,6 +968,7 @@ namespace MainWindow
 			break;
 
 		case WM_CLOSE:
+			MainThread_Stop();
 			InputDevice::StopPolling();
 			WindowsRawInput::Shutdown();
 			return DefWindowProc(hWnd,message,wParam,lParam);
@@ -976,8 +977,9 @@ namespace MainWindow
 			KillTimer(hWnd, TIMER_CURSORUPDATE);
 			KillTimer(hWnd, TIMER_CURSORMOVEUPDATE);
 			KillTimer(hWnd, TIMER_WHEELRELEASE);
+			// Main window is gone, this tells the message loop to exit.
 			PostQuitMessage(0);
-			break;
+			return 0;
 
 		case WM_USER + 1:
 			NotifyDebuggerMapLoaded();