Re: make getopt.c build in visual studio

[Eric Blake]

> With this, getopt actually do seem to compile and work in Visual
> Studio.  Tested with the CLI in libtasn1, part of GnuTLS, with long
> options.
> 
> I'll install this shortly unless someone protests.

I'm not sure about this.  Lately, the move has been to assume that
<unistd.h> exists, and this is a step backwards.  What if, instead,
you provided a unistd_.h that got installed on platforms that are
lacking (so far, only MSVS comes to mind), then make modules
that unconditionally use <unistd.h> depend on a new unistd
module?

-- 
Eric Blake