jack: reduced sleep time to 1ms

When waiting for free space in the ring buffer, the JACK plugin
sleeped 10ms until there is enough space.  This delay was too large
for low-latency setups (<10ms), and created a lot of xruns.  Work
around that by reducing the sleep time to 1ms.

A proper solution for this would be to use an event based approach,
and we will do it, just not now.

NEWS

@@ -37,6 +37,7 @@ ver 0.14.2 (2009/??/??)
 * audio outputs:
   - jack: allocate ring buffers before connecting
   - jack: clear "shutdown" flag on reconnect
+  - jack: reduced sleep time to 1ms
 
 
 ver 0.14.1 (2009/01/17)

src/output/jack_plugin.c

@@ -421,7 +421,7 @@ mpd_jack_play(void *data, const char *buff, size_t size)
 		} else {
 			/* XXX do something more intelligent to
 			   synchronize */
-			my_usleep(10000);
+			my_usleep(1000);
 		}
 
 	}