[BUG] one cannot add widgets to notebooks (regression against gtk2-perl)

[Thierry Vignaud <tvignaud mandrakesoft com>]

Gtk2::Notebook->append_page does not accept any other widgets that the
abstract base type Gtk2::Widget :

$noteboot->append_page(
                       create_scrolled_window(
                                              gtkset_size_request(
                                                                  gtkset_border_width($summary, 40),
                                                                  50, 50),
                                              ),
                        "");

makes it exit with:

Uncaught exception from user code:
        variable is not of type Gtk2::Widget at /pub/cvs/mdk/soft/control-center/control-center line 416.
Use of uninitialized value in subroutine entry at /usr/lib/libDrakX/c.pm line 10.

the return value of create_scrolled_window being
"Gtk2::Frame=HASH(0x8888548)".

i also tested scolled window (return value being
"Gtk2::ScrolledWindow=HASH(0x87bab20)").

i did not test other widgets.

there's a bug in the type checking system there...