Claws-mail all windows open in full-page

[ntrfug <ntrfug@cox.net>]

I've been using claws-mail since well before it was claws-mail (back in
the sylpheed days).

When I checked for new mail or opened dialogs they opened in
reduced size.

I upgraded to stretch a couple of months ago, and to buster just last
night. Since the stretch upgrade all claws-mail dialogs opened in
maximum size.

If I catch "Get mail" before it's finished, I can reduce the dialog to
a business-card-sized window, and that works for the current session,
but if I exit the program the dialogs return to full size whenever I
re-start.