player_thread: fix cross-fading duplicate chunk bug

When the decoder of the new song is not fast enough, the player thread
has to wait for it for a moment.  However the variable "nextChunk" was
reset to -1 during that, making the next loop iteration assume that
cross-fading has not begun yet.  This patch overwrites it with "0"
while waiting.

NEWS

@@ -12,6 +12,7 @@ ver 0.15 - (200?/??/??)
 * failure to read the state file is non-fatal
 * fix minor memory leak in decoder_tag()
 * added Icy-Metadata support
+* fix cross-fading bug: it used to play some chunks of the new song twice
 
 ver 0.14 (2008/12/25)
 * audio outputs:

src/player_thread.c

@@ -451,6 +451,14 @@ static void do_play(void)
 						music_pipe_set_lazy(false);
 						notify_signal(&dc.notify);
 						notify_wait(&pc.notify);
+
+						/* set nextChunk to a
+						   non-negative value
+						   so the next
+						   iteration doesn't
+						   assume crossfading
+						   hasn't begun yet */
+						nextChunk = 0;
 						continue;
 					}
 				}