use g_type_is_a() to check for object_type being a G_TYPE_OBJECT, not

use g_type_is_a() to check for object_type being a G_TYPE_OBJECT, not

Fri Mar  9 10:14:00 2001  Tim Janik  <timj@gtk.org>

        * gparamspecs.c (g_param_spec_object): use g_type_is_a() to check
        for object_type being a G_TYPE_OBJECT, not G_TYPE_IS_OBJECT(), since
        that wouldn't allow interface types.

        * gtype.c (g_type_interface_add_prerequisite): arg, fixed small cnp bug
        with bad implications and an off-by-one error.