fix FTBFS with Boost 1.53.0

A workaround for the bug has been suggested at
http://lists.boost.org/boost-users/2013/03/78142.php

.../halmd/mdsim/particle.cpp:60:5: error: no matching function for call to ‘transform(std::vector<unsigned int>::const_iterator&, std::vector<unsigned int>::const_iterator&, std::vector<std::basic_string<char> >::iterator&, <unresolved overloaded function type>)’