Fix locking.

(Oops, I guess this is a remnant of the original test code, that did use SDL audio ...)

stepmania/src/arch/Sound/RageSoundDriver_ALSA9.cpp

@@ -163,9 +163,8 @@ void RageSound_ALSA9::StartMixing(RageSound *snd)
 	sound *s = new sound;
 	s->snd = snd;
 
-	SDL_LockAudio();
+	LockMutex L(SOUNDMAN->lock);
 	sounds.push_back(s);
-	SDL_UnlockAudio();
 }
 
 void RageSound_ALSA9::Update(float delta)

stepmania/src/arch/Sound/RageSoundDriver_DSound_Software.cpp

@@ -103,9 +103,8 @@ void RageSound_DSound_Software::StartMixing(RageSound *snd)
 	sound *s = new sound;
 	s->snd = snd;
 
-	SDL_LockAudio();
+	LockMut(SOUNDMAN->lock);
 	sounds.push_back(s);
-	SDL_UnlockAudio();
 }
 
 void RageSound_DSound_Software::Update(float delta)

stepmania/src/arch/Sound/RageSoundDriver_Null.cpp

@@ -89,9 +89,8 @@ void RageSound_Null::StartMixing(RageSound *snd)
 	sound *s = new sound;
 	s->snd = snd;
 
-	SDL_LockAudio();
+	LockMutex L(SOUNDMAN->lock);
 	sounds.push_back(s);
-	SDL_UnlockAudio();
 }
 
 void RageSound_Null::Update(float delta)

stepmania/src/arch/Sound/RageSoundDriver_WaveOut.cpp

@@ -115,9 +115,8 @@ void RageSound_WaveOut::StartMixing(RageSound *snd)
 	sound *s = new sound;
 	s->snd = snd;
 
-	SDL_LockAudio();
+	LockMutex L(SOUNDMAN->lock);
 	sounds.push_back(s);
-	SDL_UnlockAudio();
 }
 
 void RageSound_WaveOut::Update(float delta)