* message.texi (Movement): message-beginning-of-line.

* message.texi (Movement): message-beginning-of-line.

* message.el (message-point-in-header-p): New function.
(message-do-auto-fill): Use it.
(message-beginning-of-line): New function.  Goes to beginning of
header value (i.e., end of header name), or to beginning of line
if already at beginning of value.
(message-mode-map): Bind it.