Right-to-left GUI in pretest

[Per Starbäck]

Using a locale with right-to-left writing, for example

  LANG=ar_EG.utf8 src/emacs-24.0.93.1

I get the menu-bar and the tool-bar in the reverse direction, that is
with the Help menu on the left and the File menu on the right, for
example.
This is a GTK thing. At least with  ./configure --with-x-toolkit=motif
 it's not like this.

If emacs was localized with non-English menus this would be good, but
since these things are in English anyway I think it only looks
strange.
(Also the mirroring affects the meanings of the values left and right
for tool-bar-position.)