Re: NSDocument localization patch

[Nicola Pero]

> Hi,
> 
> Here is just a small patch for NSDocument*.m that fixes "localize" fixmes.
> 
> New Localizable.string has to be generated (using make_strings).

Hi Stefan, thanks!

I committed your changes, and/but extended your idea of redefining _() to
be a wrapper for GSGuiLocalizedString to be used in all gnustep-gui.

I also reorganized most of the package so that we now take (finally :-)
advantage of this new wonderful make_strings package to mechanically
manage localizable strings in gnustep-gui.

I'm of course planning to build more extensive support for all this stuff
(make_strings, and localization of libraries) in gnustep-make; but I
thought I'd prefer to first play around and experiment with it in some
real world examples ... one of them is, of course, gnustep-gui :-)