bug#4524: 23.1.50; Fullscreen mode layout fixed (Reopen of bug#4363)

> There is no no-mans-land for the Gtk-version of Emacs. This fixes it for the
> Lucid-version:

But there are other problems with the Gtk-version that causes me to
use the --without-toolkit-scroll-bars option.

I.e. you cannot do precise positioning.  Also you cannot undo precisely
a page-next.  This is very useful, in particular if you are not sitting
in front of the screen but helping someone out - using only the mouse.

Here is a nice explanation of these features:
http://www.complang.tuwien.ac.at/anton/athena-scrollbars