Fix from "B.V.Dean" <B.V.Dean@ukc.ac.uk> to add "dos filemode" parameter

Fix from "B.V.Dean" <B.V.Dean@ukc.ac.uk> to add "dos filemode" parameter
to allow a chmod to be done if the user has write access to a file, just
like Windows allows. Off by default (compare with "dos filetimes" parameter).
Jeremy.
(This used to be commit 8abdf0e29fdb02a7929aa4395947b5023a7194a0)