thread/Name: set thread names

For debugging.

src/OutputThread.cxx

@@ -31,6 +31,7 @@
 #include "MusicPipe.hxx"
 #include "MusicChunk.hxx"
 #include "thread/Util.hxx"
+#include "thread/Name.hxx"
 #include "system/FatalError.hxx"
 #include "util/Error.hxx"
 #include "Log.hxx"
@@ -579,6 +580,8 @@ audio_output_task(void *arg)
 {
 	struct audio_output *ao = (struct audio_output *)arg;
 
+	FormatThreadName("output:%s", ao->name);
+
 	SetThreadRealtime();
 
 	ao->mutex.lock();