Stop Movie/Netplay before triggering STM shutdown

This fixes a bug which caused Movie (input recording or playback) or
netplay not to be stopped. DolphinWX previously triggered a STM power
event, and then the STM directly stopped the emulation; the code
which stops Movie/Netplay was completely skipped.

This is fixed by moving it /before/ sending the shutdown event.

Source/Core/DolphinWX/Frame.h

@@ -90,6 +90,7 @@ public:
 
   void DoPause();
   void DoStop();
+  bool TriggerSTMPowerEvent();
   void OnStopped();
   void DoRecordingSave();
   void UpdateGUI();