gplugin/gplugin

Add gir targets to the dependencies sources attribute and other meson cleanups.

Adding the gir targs to the dependency object of the library allows us to be
able to use the dependency in a gnome.generate_gir for a library that consumes
our api regardless of if it's a system install or a subproject.

Testing Done:
Modified the gplugin subproject in pidgin and used these changes to verify that it fixed the current build issues over there.

Reviewed at https://reviews.imfreedom.org/r/939/
/*
* Copyright (C) 2011-2020 Gary Kramlich <grim@reaperworld.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <https://www.gnu.org/licenses/>.
*/
#ifndef GPLUGIN_GTK_VIEWER_WINDOW_H
#define GPLUGIN_GTK_VIEWER_WINDOW_H
#include <glib.h>
#include <glib-object.h>
#include <gtk/gtk.h>
#define GPLUGIN_GTK_VIEWER_TYPE_WINDOW (gplugin_gtk_viewer_window_get_type())
G_DECLARE_FINAL_TYPE(
GPluginGtkViewerWindow,
gplugin_gtk_viewer_window,
GPLUGIN_GTK_VIEWER,
WINDOW,
GtkWindow)
G_BEGIN_DECLS
GtkWidget *gplugin_gtk_viewer_window_new(void);
G_END_DECLS
#endif /* GPLUGIN_GTK_VIEWER_WINDOW_H */