fix AccumStageStats doesn't get cleared between games

stepmania/src/GameState.cpp

@@ -190,7 +190,7 @@ void GameState::Reset()
 	 * SongManager::UpdateBest could be called).  Erase the cache. */
 	SONGMAN->RegenerateNonFixedCourses();
 
-	STATSMAN->m_vPlayedStageStats.clear();
+	STATSMAN->Reset();
 
 	m_SongOptions.Init();
 	

stepmania/src/StatsManager.h

@@ -10,6 +10,12 @@ class StatsManager
 public:
 	StatsManager();
 
+	void Reset()
+	{
+		m_vPlayedStageStats.clear();
+		CalcAccumStageStats();
+	}
+
 	StageStats	m_CurStageStats;				// current stage (not necessarily passed if Extra Stage)
 	vector<StageStats>	m_vPlayedStageStats;