bug#10080: 23.3; Rmail shows an extra blank line at the end when displaying a non-MIME message

[Mark Lillibridge]

    This is easy to reproduce; just send yourself a plain text message
that has no extra blank lines after it.  Incorporate it into Rmail and
notice that it is displayed with an extra blank line.  For example,

> Date: Sat, 19 Nov 2011 12:05:50 -0800
> Subject: no blank lines follow
> From: Mark Lillibridge <lillibridge@gmail.com>
> To: mdl@alum.mit.edu
> 
> this is the only line
> 

where I have added "> " before each line of the displayed message.  If
you check the underlying mbox file, you'll see that indeed, "this is the
only line" is the last line of that message.  (Remember that messages in
mbox format start with a "From " line and are followed by a blank
separator line that does not count as part of the message.)  This extra
blank line is not displayed for MIME messages

    The fix should be pretty easy; just make sure to check that any
other code that might be relying on the contents of the decoded buffer
(output as seen, edit?) doesn't get broken.

- Mark