(rmail-decode-babyl-format):

(rmail-decode-babyl-format):
Set save-buffer-coding-system instead of buffer-file-coding-system.
Decode the whole Babyl text at once, not message by message.
Don't alter global value of rmail-file-coding-system.
(rmail-show-message): Set buffer-file-coding-system from
X-Coding-System header field.
(rmail-convert-to-babyl-format): Record X-Coding-System header
for each message that was converted.
(rmail-variables): Make local binding for save-buffer-coding-system,
and set it from buffer-file-coding-system if not already non-nil.

(rmail-ignored-headers): Ignore X-Coding-System header.
Ignore Return-Path, Errors-To, X-Attribution, X-Disclaimer.