call SONGMAN->SetPreferences when PREFSMAN->m_bAutogenSteps

changes

stepmania/src/ScreenOptionsMaster.cpp

@@ -563,6 +563,9 @@ void ScreenOptionsMaster::ExportOptions()
 		SOUNDMAN->SetPrefs( PREFSMAN->m_fSoundVolume );
 	}
 	
+	if( ChangeMask & OPT_APPLY_SONG )
+		SONGMAN->SetPreferences();
+
 	CHECKPOINT;
 }
 

stepmania/src/ScreenOptionsMasterPrefs.cpp

@@ -520,6 +520,7 @@ int ConfOption::GetEffects() const
 		{ WaitForVsync,			OPT_APPLY_GRAPHICS },
 		{ GameSel,				OPT_RESET_GAME },
 		{ SoundVolume,			OPT_APPLY_SOUND },
+		{ AutogenSteps,			OPT_APPLY_SONG },
 	};
 
 	int ret = OPT_SAVE_PREFERENCES;

stepmania/src/ScreenOptionsMasterPrefs.h

@@ -7,6 +7,7 @@ static const int MAX_OPTIONS=16;
 #define OPT_APPLY_THEME					0x4
 #define OPT_RESET_GAME					0x8
 #define OPT_APPLY_SOUND					0x16
+#define OPT_APPLY_SONG					0x32
 
 struct ConfOption
 {