FPSCounter: Flush the logs every second and close them when the renderer is shut down.

Source/Core/VideoCommon/FPSCounter.h

@@ -9,6 +9,9 @@ namespace FPSCounter
 // Initializes the FPS counter.
 void Initialize();
 
+// Shutdown the FPS counter by closing the logs.
+void Shutdown();
+
 // Called when a frame is rendered. Returns the value to be displayed on
 // screen as the FPS counter (updated every second).
 int Update();