A comment in boost/iterator.hpp and boost/detail/iterator.hpp mentions that
the files are obsolete and will be deprecated. All they do is pull some types
from namespace std into namespace boost.
This change excludes boost:: and boost::detail:: namespaces from ADL for unqualified function calls (e.g. algorithms). This reduces the possibility of name clashes with other libraries and user's code. One of the effects should be fixing test failures on gcc 4.2 and 4.4 due to clashed with Boost.TypeTraits.
Also some of the functions marked with inline keyword.
