Make rmail-default-dont-reply-to-names nil (Bug#7888); rename rmail-dont-reply-*.

Make rmail-default-dont-reply-to-names nil (Bug#7888); rename rmail-dont-reply-*.

* lisp/mail/mail-utils.el (mail-dont-reply-to-names): New variable,
from rmail-dont-reply-to-names.  Callers changed.
(mail-dont-reply-to): Rename from mail-dont-reply-to.
(rmail-dont-reply-to): Make it an obsolete alias.

* lisp/mail/rmail.el (rmail-default-dont-reply-to-names): Default to
nil, and make obsolete.
(rmail-dont-reply-to-names): Alias to mail-dont-reply-to-names.

* lisp/mail/rmailsum.el (rmail-summary-sort-by-correspondent): Doc fix.

* lisp/mail/rmailsort.el (rmail-sort-by-correspondent)
(rmail-select-correspondent): Doc fix.  Use mail-dont-reply-to.

* lisp/mail/rmail.el (rmail-reply): Use mail-dont-reply-to.