Kea uses deprecated header

In file included from /usr/include/boost/math/common_factor.hpp:13,
                 from ../../../../src/lib/util/encode/base_n.cc:21:
/usr/include/boost/math/common_factor_ct.hpp:16:63: note: #pragma message: This header is deprecated. Use <boost/integer/common_factor_ct.hpp> instead.
 BOOST_HEADER_DEPRECATED("<boost/integer/common_factor_ct.hpp>");
                                                               ^
In file included from /usr/include/boost/math/common_factor.hpp:14,
                 from ../../../../src/lib/util/encode/base_n.cc:21:
/usr/include/boost/math/common_factor_rt.hpp:13:63: note: #pragma message: This header is deprecated. Use <boost/integer/common_factor_rt.hpp> instead.
 BOOST_HEADER_DEPRECATED("<boost/integer/common_factor_rt.hpp>");
                                                               ^
In file included from ../../../../src/lib/util/encode/base_n.cc:21:
/usr/include/boost/math/common_factor.hpp:16:60: note: #pragma message: This header is deprecated. Use <boost/integer/common_factor.hpp> instead.
 BOOST_HEADER_DEPRECATED("<boost/integer/common_factor.hpp>");
                                                            ^