song_update: convert to C++

Makefile.am

@@ -309,7 +309,7 @@ src_mpd_SOURCES = \
 	src/replay_gain_info.c \
 	src/sig_handlers.c \
 	src/Song.cxx \
-	src/song_update.c \
+	src/SongUpdate.cxx \
 	src/SongPrint.cxx src/SongPrint.hxx \
 	src/SongSave.cxx src/SongSave.hxx \
 	src/resolver.c src/resolver.h \

src/song_update.c → src/SongUpdate.cxx

 /*
- * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -18,9 +18,15 @@
  */
 
 #include "config.h" /* must be first for large file support */
+
+extern "C" {
 #include "song.h"
 #include "uri.h"
+}
+
 #include "directory.h"
+
+extern "C" {
 #include "mapper.h"
 #include "decoder_list.h"
 #include "decoder_plugin.h"
@@ -29,6 +35,7 @@
 #include "tag.h"
 #include "tag_handler.h"
 #include "input_stream.h"
+}
 
 #include <glib.h>
 
@@ -187,7 +194,7 @@ song_file_update_inarchive(struct song *song)
 	if (suffix == NULL)
 		return false;
 
-	plugin = decoder_plugin_from_suffix(suffix, false);
+	plugin = decoder_plugin_from_suffix(suffix, nullptr);
 	if (plugin == NULL)
 		return false;