clean up memory card logic:

- Don't do the OS mount for cards during the attract screens.  Only do OS mounts in the time between BeginGame and PlayersFinalized.
 - Remove logic for fast load of a Profile from the MemoryCard.  Instead, load the whole profile all at once on PlayersFinalized.

stepmania/src/arch/MemoryCard/MemoryCardDriver_Null.h

@@ -17,6 +17,7 @@ public:
 	virtual void UnPauseMountingThread() {}
 	virtual void DoOsMount() {}
 	virtual void DontDoOsMount() {}
+	virtual void SetMountThreadState( MountThreadState mts ) {}
 };
 
 #endif