Make some APIs that return struct introspectable

In order to do this, we need to define some boxed types. So we need
to add a new dependency, GObject, to GTop.

https://bugzilla.gnome.org/show_bug.cgi?id=663265

lib/boxed.c

@@ -0,0 +1,47 @@
+/* Copyright (C) 2011 Red Hat
+   This file is part of LibGTop 1.0.
+
+   Contributed by Jasper St. Pierre <jstpierre@mecheye.net>, November 2011
+
+   LibGTop 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.
+
+   LibGTop 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 LibGTop; see the file COPYING. If not, write to the
+   Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.
+*/
+
+#include <glibtop.h>
+#include <glibtop/mountlist.h>
+#include <glibtop/procmap.h>
+#include <glibtop/procopenfiles.h>
+
+#define DEFINE_BOXED(type)                              \
+    static type *                                       \
+    type##_copy (type *p)                               \
+    {                                                   \
+        type *n = g_new (type, 1);                      \
+        memcpy (n, p, sizeof (type));                   \
+        return n;                                       \
+    }                                                   \
+                                                        \
+    G_DEFINE_BOXED_TYPE (type,                          \
+                         type,                          \
+                         type##_copy,                   \
+                         g_free)
+
+DEFINE_BOXED (glibtop);
+DEFINE_BOXED (glibtop_map_entry);
+DEFINE_BOXED (glibtop_proc_map);
+DEFINE_BOXED (glibtop_open_files_entry);
+DEFINE_BOXED (glibtop_proc_open_files);
+DEFINE_BOXED (glibtop_mountentry);
+DEFINE_BOXED (glibtop_mountlist);