[PATCH, v4] Use cygwin spawn functions

[DJ Delorie]

> Which happened, somehow, in the testsuite.

Ick?  ;-)

> > Look in setenv.c for how to deal with the "environ" variable.  You
> > can't just declare it.
> 
> I didn't add or change that.  It's pre-existing in that file.

Hmmm... so it was.

> *shrug* Today's Cygwin still does not have _spawn*.  Given that
> this file is *not* used with mingw, and thus the Microsoft rtl,
> it hardly seems worthwhile.

I suppose, until cygwin "catches up".  I suppose we can fix it then.