Windows: Check for devices on Windows events only.

A user reported stuttering after the periodic checks, and devices failing
until unplug/replug.  Presumably, this is caused by poor drivers reacting
badly to periodic DirectInput queries, so less queries should help.

Windows/MainWindow.cpp

@@ -54,6 +54,7 @@
 #include "Windows/GEDebugger/GEDebugger.h"
 
 #include "Windows/main.h"
+#include "Windows/DinputDevice.h"
 #include "Windows/EmuThread.h"
 #include "Windows/resource.h"
 
@@ -814,6 +815,10 @@ namespace MainWindow
 		case WM_CHAR:
 			return WindowsRawInput::ProcessChar(hWnd, wParam, lParam);
 
+		case WM_DEVICECHANGE:
+			DinputDevice::CheckDevices();
+			return DefWindowProc(hWnd, message, wParam, lParam);
+
 		case WM_VERYSLEEPY_MSG:
 			switch (wParam) {
 			case VERYSLEEPY_WPARAM_SUPPORTED: