Prep work for cache tag adjusting.

Hopefully this won't take too long.

src/Song.cpp

@@ -69,6 +69,9 @@ Song::Song()
 	m_fMusicSampleStartSeconds = -1;
 	m_fMusicSampleLengthSeconds = DEFAULT_MUSIC_SAMPLE_LENGTH;
 	m_fMusicLengthSeconds = 0;
+	firstSecond = -1;
+	lastSecond = -1;
+	specifiedLastSecond = -1;
 	m_fFirstBeat = -1;
 	m_fLastBeat = -1;
 	m_fSpecifiedLastBeat = -1;

src/Song.h

@@ -232,6 +232,9 @@ public:
 	RString	m_sInstrumentTrackFile[NUM_InstrumentTrack];
 
 	float	m_fMusicLengthSeconds;
+	float firstSecond;
+	float lastSecond;
+	float specifiedLastSecond;
 	float	m_fFirstBeat;	// beat of first note
 	float	m_fLastBeat;	// beat of last note
 	float	m_fSpecifiedLastBeat;	// specified last beat of the song