bos: remove smail-notifier

bos: remove smail-notifier

smail-notifier is a sample program that is undocumented and has not
been well maintained.  It produces copious compiler warnings, and
would require effort to bring the code up to decent coding practices.

The bosserver provides a -notifier feature that can be used for
notifications, but that feature does not depend on this sample program.

Removed the code, cleaned up the Makefiles and .gitignore.

Reviewed-on: https://gerrit.openafs.org/13509
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 6e988a5b3900fe73c314c9960d6fb7753ff98411)

Change-Id: I073a2b772f894e321bd0b41e012229c8e6d3105c
Reviewed-on: https://gerrit.openafs.org/13738
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>