pidgin/pidgin

use a globally unique id when creating new Pidgin::DisplayItem's

Use a globally unique id when creating new `Pidgin::DisplayItem`s as the doc demands and as discussed on [discourse](https://discourse.imfreedom.org/t/how-is-pidgin-id-supposed-to-be-unique/134/2)

Testing Done:
Ran Pidgin and opened a conversation.

Reviewed at https://reviews.imfreedom.org/r/2980/
/*
* Purple - Internet Messaging Library
* Copyright (C) Pidgin Developers <devel@pidgin.im>
*
* 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, see <https://www.gnu.org/licenses/>.
*/
#ifndef PURPLE_XMPP_CORE_H
#define PURPLE_XMPP_CORE_H
#include <glib.h>
#define PURPLE_XMPP_DOMAIN (g_quark_from_static_string("xmpp-plugin"))
#endif /* PURPLE_XMPP_CORE_H */