db/Error: remove unused variable db_domain

Makefile.am

@@ -224,7 +224,7 @@ libmpd_a_SOURCES += \
 	src/db/DatabasePrint.cxx src/db/DatabasePrint.hxx \
 	src/db/DatabaseQueue.cxx src/db/DatabaseQueue.hxx \
 	src/db/DatabasePlaylist.cxx src/db/DatabasePlaylist.hxx \
-	src/db/DatabaseError.cxx src/db/DatabaseError.hxx \
+	src/db/DatabaseError.hxx \
 	src/db/DatabaseLock.cxx src/db/DatabaseLock.hxx \
 	src/db/DatabasePlugin.hxx \
 	src/db/Interface.hxx \
@@ -1709,7 +1709,6 @@ test_DumpDatabase_LDADD = \
 test_DumpDatabase_SOURCES = test/DumpDatabase.cxx \
 	src/protocol/Ack.cxx \
 	src/Log.cxx src/LogBackend.cxx \
-	src/db/DatabaseError.cxx \
 	src/db/Registry.cxx \
 	src/db/Selection.cxx \
 	src/db/PlaylistVector.cxx \

src/db/DatabaseError.cxx

@@ -1,24 +0,0 @@
-/*
- * Copyright 2003-2016 The Music Player Daemon Project
- * 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.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
-
-#include "config.h"
-#include "DatabaseError.hxx"
-#include "util/Domain.hxx"
-
-const Domain db_domain("db");

src/db/DatabaseError.hxx

@@ -22,8 +22,6 @@
 
 #include <stdexcept>
 
-class Domain;
-
 enum class DatabaseErrorCode {
 	/**
 	 * The database is disabled, i.e. none is configured in this
@@ -48,6 +46,4 @@ public:
 	}
 };
 
-extern const Domain db_domain;
-
 #endif