Improve Reply-to vs From comparison when replying. (closes #3909)

Improve Reply-to vs From comparison when replying. (closes #3909)

Prior to this patch, if the Reply-to mailbox matched the From mailbox,
mutt would always use the From address.  This was probably done to
preserve the display name, as the Reply-to address is often missing one.

Unfortunately, there are circumstances where the Reply-to display-name
has significance, such as in ticket 3909.

Change mutt so that it only uses the From address if the Reply-To has
no display-name.