* lisp/pop3.el (pop3-movemail): Use `write-region-as-binary' instead of

* lisp/pop3.el (pop3-movemail): Use `write-region-as-binary' instead of
`append-to-file'.
(pop3-movemail-file-coding-system): Abolished.

* lisp/nnheader.el (nnheader-find-file-noselect): Use
`find-file-noselect-as-specified-coding-system' instead of
`find-file-noselect'.

* lisp/nnmail.el (nnmail-find-file): Use
`insert-file-contents-as-specified-coding-system' instead of
`insert-file-contents'.
* lisp/nnheader.el (nnheader-insert-file-contents): Likewise.

* lisp/message.el (message-send-mail-with-qmail): Enclose
`call-process-region' with `as-binary-process'.
(message-send-mail-with-sendmail): Likewise.
(message-send-coding-system): Abolished.

* lisp/gnus-start.el (gnus-save-newsrc-file): Emulate `save-buffer' with
`write-region-as-specified-coding-system'.
(gnus-read-newsrc-el-file): Emulate `load' with
`insert-file-contents-as-specified-coding-system' and `eval-region'.

* lisp/gnus-cache.el (gnus-cache-save-buffers): Use
`gnus-write-buffer-as-specified-coding-system' instead of `gnus-write-buffer'.

* lisp/gnus-util.el (gnus-output-to-mail): Use `write-region-as-binary'
instead of `append-to-file'.
(gnus-output-to-mail): Use `gnus-write-buffer-as-binary' instead of
`gnus-write-buffer'.
(gnus-write-buffer-as-specified-coding-system): New function.
(gnus-write-buffer-as-binary): New function.

* lisp/nnmail.el (nnmail-write-region): Use
`write-region-as-specified-coding-system' instead of `write-region'.
* lisp/gnus-start.el (gnus-save-newsrc-file): Likewise.
* lisp/gnus-agent.el (gnus-agent-expire): Likewise.
(gnus-agent-fetch-headers): Likewise.
(gnus-agent-flush-cache): Likewise.
(gnus-agent-fetch-articles): Likewise.
(gnus-agent-save-history): Likewise.
(gnus-agent-save-groups): Likewise.
(gnus-agent-save-active): Likewise.