Update maintainer list.

libs/maintainers.txt

@@ -118,6 +118,7 @@ smart_ptr             Peter Dimov <pdimov -at- pdimov.com>
 smart_ptr/make_shared Glen Fernandes <glenfe -at- live.com>
 sort                  Steven Ross <spreadsort -at- gmail.com>
 spirit                Joel de Guzman <joel -at- boost-consulting.com>, Hartmut Kaiser <hartmut.kaiser -at- gmail.com>
+stacktrace            Antony Polukhin <antoshkka -at- gmail.com>
 statechart            Andreas Huber <ahd6974-boostorg -at- yahoo.com>
 static_assert         John Maddock <john -at- johnmaddock.co.uk>
 test                  Gennadiy Rozental <rogeeff -at- gmail.com>, Raffi Enficiaud <raffi.enficiaud -at- free.fr>