mailmap: Dmitry Smirnov is with Debian GNU/Linux

Reviewed-by: Dmitry Smirnov <onlyjob@member.fsf.org>
Signed-off-by: Loic Dachary <loic@dachary.org>
mailmap: Derek Yarnell is with University of Mississippi

Signed-off-by: Loic Dachary <loic@dachary.org>