output: added audio_output_get_name()

Reduce direct accesses to the audio_output struct from the plugins:
this time, eliminate all accesses to audio_output.name.  The name is
required by some plugins for log messages.

src/Makefile.am

@@ -114,6 +114,7 @@ mpd_SOURCES = \
 	notify.c \
 	audio.c \
 	audioOutput.c \
+	output_api.c \
 	output_list.c \
 	output_thread.c \
 	output_control.c \

src/audioOutputs/audioOutput_ao.c

@@ -100,7 +100,7 @@ static int audioOutputAo_initDriver(struct audio_output *audioOutput,
 	}
 
 	DEBUG("using ao driver \"%s\" for \"%s\"\n", ai->short_name,
-	      audioOutput->name);
+	      audio_output_get_name(audioOutput));
 
 	blockParam = getBlockParam(param, "options");
 

src/output_api.c

@@ -0,0 +1,24 @@
+/* the Music Player Daemon (MPD)
+ * Copyright (C) 2008 Max Kellermann <max@duempel.org>
+ * This project's homepage is: http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "output_api.h"
+
+const char *audio_output_get_name(const struct audio_output *ao)
+{
+	return ao->name;
+}

src/output_api.h

@@ -99,4 +99,6 @@ struct audio_output {
 
 extern struct notify audio_output_client_notify;
 
+const char *audio_output_get_name(const struct audio_output *ao);
+
 #endif