As the summary says, this allows using g_autoptr(GtkTreePath). This is
useful for API that uses out parameters for GtkTreePath that need to be
freed.
https://bugzilla.gnome.org/show_bug.cgi?id=791234
These complicate a lot of GdkWindow internals to implement features
that not a lot of apps use, and will be better achieved using gsk.
So, we just drop it all.
* Cover letter
Having a single header file for all autocleanups definitions was a
reasonable stop-gap measure, but now GTK+ is starting to use G_DECLARE_*
macros. This means that every class using a G_DECLARE_* macro will need
to include "gtk.h" to avoid compiler warnings, which is not acceptable.
By moving the G_DEFINE_AUTO* use to the header that defines the type we
allow using the G_DECLARE_* macros without sacrificing the ability to
include only the needed files when deriving from a class.
* Commit
This commit changes all includes relative to GtkWindow to define their
own autocleanup macros.
