fixed wrong dialog window position.
place some dialogs at the center on parent window.
make input dialog in front on focus out.
create/destroy input dialog each time it is displayed.
adjusted the minimum input dialog size.
modified the text of mailbox setup dialog.
made the order of buttons comply with GNOME HIG.
reimplemented summary view with GtkTreeView.
replaced intl.h with glib/gi18n.h.
use GTK stock button for dialog button set.
Initial import of Sylpheed (GTK2 version).