Sync with `t-gnus-6_14'

Sync with `t-gnus-6_14'
-----------------------
* message.el (message-forward, message-indent-citation): Replace the use of
`eolp' with `bolp' for detecting the start of the line.

Sync with Gnus
--------------
* gnus-uu.el (gnus-uu-save-article): Don't insert text/plain tag; don't insert
digest header when forwarding.
(gnus-uu-digest-mail-forward): Replace the use of `message-forward' with
`message-mail' and `message-news'.
(gnus-uu-digest-headers): Add User-Agent and X-Face.

* gnus-sum.el (gnus-summary-post-menu): Replace the use of
`gnus-summary-post-digest' and `gnus-summary-mail-digest' with
`gnus-uu-digest-post-forward' and `gnus-uu-digest-mail-forward'.

* gnus-msg.el (gnus-summary-post-digest, gnus-summary-mail-digest): Comment.
(gnus-summary-send-map): Replace the use of `gnus-summary-post-digest' and
`gnus-summary-mail-digest' with `gnus-uu-digest-post-forward' and
`gnus-uu-digest-mail-forward'.