Don't re-read game prefs at reset; it's a hack to load game prefs

and mappings after changing the game.  Do it in ChangeCurrentGame
instead.  Don't expose ReadGamePrefsFromDisk.  (This code path
is still a little overcomplicated, but it's a bit simpler now ...)

stepmania/src/StepMania.h

@@ -12,7 +12,6 @@ void ApplyGraphicOptions();
 void NORETURN HandleException( CString error );
 void ExitGame();
 void ResetGame( bool ReturnToFirstScreen=true );
-void ReadGamePrefsFromDisk( bool bSwitchToLastPlayedGame=true );
 void SaveGamePrefsToDisk();
 void ChangeCurrentGame( const Game* g );
 void FocusChanged( bool bHasFocus );