Use @file for buffers, per the Texinfo manual

Use @file for buffers, per the Texinfo manual

* doc/misc/ada-mode.texi, doc/misc/auth.texi, doc/misc/calc.texi:
* doc/misc/ebrowse.texi, doc/misc/efaq.texi, doc/misc/emacs-gnutls.texi:
* doc/misc/epa.texi, doc/misc/ert.texi, doc/misc/eshell.texi:
* doc/misc/eww.texi, doc/misc/flymake.texi, doc/misc/gnus.texi:
* doc/misc/info.texi, doc/misc/message.texi, doc/misc/mh-e.texi:
* doc/misc/newsticker.texi, doc/misc/pcl-cvs.texi, doc/misc/rcirc.texi:
* doc/misc/sem-user.texi, doc/misc/smtpmail.texi, doc/misc/url.texi:
* doc/misc/viper.texi, doc/misc/wisent.texi, doc/misc/woman.texi:
Use @file for buffers, per the Texinfo manual.