dummy.cxx: remove unused file

This file was used previously to force C++ linkage.
It's no longer required because most of the code is C++ anyway.

src/dummy.cxx

@@ -1,30 +0,0 @@
-/*
- * Copyright (C) 2003-2011 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.
- */
-
-/*
- * Just a dummy C++ file that is linked to work around an automake
- * bug: automake uses CXXLD when at least one source is C++, but when
- * you link a static library with a C++ source, it uses CCLD.  This
- * causes linker problems (undefined reference to 'operator
- * delete(void*)'), because CCLD does not link with libstdc++.
- *
- * By linking with this empty C++ source, automake decides to use
- * CXXLD.
- *
- */