Reset fade booleans when halting music

This fixes the 2.2-and-below music blocking workaround not working in
2.3.

The issue was that when the music got halted by the script, the fade
volume would still be processing, silently being decremented in the
background. So the script playing the track afterwards would make the
game queue it (as it was called during the fade), but then the music is
halted so the game would attempt to play it, but the fade is STILL
happening so it wouldn't actually play it and would attempt to queue the
track again.

However, that queue gets discarded immediately afterwards because the
music.play() call happened inside the code responsible for playing the
queued music, and that code unconditionally clears the queue variables
immediately after calling play(). So that's good to know - if the game
queues a song, but fails to play it because of a fade, it's not going to
immediately re-queue it and potentially get stuck in a loop of
infinitely queueing the same song over and over again each frame.

Anyways, the source of the problem is not resetting the fade booleans
when halting music, so I've reset them.

Fixes #701.

desktop_version/src/Music.cpp

@@ -268,6 +268,8 @@ void musicclass::haltdasmusik(void)
 	/* Just pauses music. This is intended. */
 	pause();
 	currentsong = -1;
+	m_doFadeInVol = false;
+	m_doFadeOutVol = false;
 }
 
 void musicclass::silencedasmusik(void)