Along the same lines as g_clear_object(), g_set_object() is a
convenience function to update a GObject pointer, handling reference
counting transparently and correctly.
Specifically, it handles the case where a pointer is set to its current
value. If handled naïvely, that could result in the object instance
being finalised. In the following code, that happens when
(my_obj == new_value) and the object has a single reference:
g_clear_object (&my_obj);
my_obj = g_object_ref (new_value);
It also simplifies boilerplate code such as set_property()
implementations, which are otherwise long and boring.
Test cases included.
https://bugzilla.gnome.org/show_bug.cgi?id=741589
Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
