close confirm dialog: max width for labels

So the labels are not too long.

Calling gtk_window_set_default_size() with a reasonable size doesn't
work, because the natural size of the labels have a higher priority.

https://bugzilla.gnome.org/show_bug.cgi?id=730693
close confirm dialog: max width for labels (multiple docs)

https://bugzilla.gnome.org/show_bug.cgi?id=730693
File browser: fix GeditView grab focus when opening a file

All the details:
https://bugzilla.gnome.org/show_bug.cgi?id=706900