Cygwin: setrlimit: Add a permission check

Cygwin: setrlimit: Add a permission check

If the incoming soft limit is less restrictive than the current
hard limit, bail out with EPERM.  Given the previous sanity check,
this implies trying to raise the hard limit.  While, theoretically,
this should be allowed for privileged processes, Windows has no
matching concept in terms of job limits

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>