[PATCH] unexec() for Cygwin port

[Joe Buehler]

Below is a final set of patches to complete the Cygwin port for 21.3.50
that I did about a year ago.  These patches add unexec() support for
Cygwin, which is currently missing in CVS.

The original unexec() code I submitted was from xemacs and was rejected
for licensing reasons.  The below code is a rewrite by me that is also
much simpler and easier to understand than the xemacs code.

Please commit it to CVS as soon as possible...

Thanks.
--
Joe Buehler