prevent gdk_init() from segfaulting when invoked with (NULL, NULL); (this

prevent gdk_init() from segfaulting when invoked with (NULL, NULL); (this

Wed Jun 10 06:25:17 1998  Tim Janik  <timj@gtk.org>

        * gdk/gdk.c (gdk_init): prevent gdk_init() from segfaulting when
        invoked with (NULL, NULL); (this worked sometime ago).

        * gtk/gtktypeutils.h:
        * gtk/gtktypeutils.c: enum and flags type creation can now be done
        through gtk_type_register_enum() and gtk_type_register_flags(),
        which allow to specify the enum value arrays directly.
        the NULL terminated value arrays can be retrived through
        gtk_type_enum_get_values() and gtk_type_flags_get_values();
        (gtk_type_children_types): new function to query derived types.