[RFA/NEWS] Document the addition of a new native port: x86_64/MinGW

[Joel Brobecker]

> > 2009-01-15  Joel Brobecker  <brobecker@adacore.com>
> > 
> >         * NEWS: Document x86_64/MinGW as a new native configuration.
> > 
> > OK to commit?
> 
> Yes, and thanks.

Thanks! Now checked in.

-- 
Joel