contrib: create static library for elfparser

I want to move a bunch of this "contrib" style sources into their own
area so we can statically link them but keep them separate from main
sysprof code.

contrib/elfparser/demangle.h

@@ -0,0 +1,28 @@
+/* demangle.h
+ *
+ * Copyright 2016-2019 Christian Hergert <chergert@redhat.com>
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <glib.h>
+
+G_BEGIN_DECLS
+
+G_GNUC_INTERNAL
+gchar *sysprof_cplus_demangle (const gchar *name);
+
+G_END_DECLS