bug#17488: 24.3; mail-sendmail-undelimit-header doesn't respect mail-header-separator

[Katsumi Yamaoka]

Hi,

This is probably a rare case, so I'm not sure if it's worth
fixing, though.  If one sets `mail-header-separator' to

"                                       ."

it causes a mail corruption.  It is because `rfc822-goto-eoh'
doesn't respect `mail-header-separator' and the first line of
a message body, rather than the separator, is deleted.

`smtpmail-send-it' and `mailclient-send-it' use it by way of
`mail-sendmail-undelimit-header'.  And `sendmail-send-it' uses
it by way of `mail-header-end'.

Thanks.