(tar-mode): Locally bind next-line-add-newlines to nil.

(tar-mode): Locally bind next-line-add-newlines to nil.
(tar-subfile-mode): Doc fix.
(tar-expunge): Make questions and messages start with upper case letter.
(tar-summarize-buffer): Ditto.
(tar-subfile-save-buffer): Make message like others.
(tar-mode): Locally bind local-write-file-hooks.
(tar-mode-write-file): Renamed from tar-mode-maybe-write-tar-file.
(tar-mode-write-file): Simplify to only work for tar file buffers.
(write-file-hooks): Don't modify this.