bug#28671: 25.2; double transfer-encoding in rmailedit for complex mime messages

[Ken Olum]

Here is a test file.  Edit the first message and make some change (e.g.,
to the subject header).  Then the body will end up base64 encoded
twice.  If you then go to the next message, the headers will have extra
lines at the top due to marker problems.  The patch should fix these
problems.

Here's a new patch with the simplified code as you suggested, and
here's a change log entry:

----------------------------------------------------------------------
2017-10-02  Ken Olum  <kdo@cosmos.phy.tufts.edu>

        Fix problems when editing raw message (Bug#28671)

        * lisp/mail/rmailedit.el (rmail-cease-edit): if rmail-old-mime-state
        is set, meaning that we are editing the raw message, do not
        encode it again.  Delete old body after, not before, inserting
        new, to avoid moving marker at beginning of next message.
----------------------------------------------------------------------

                                        Ken

rmail-test
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rmailedit.patch
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