[boost] Attn: Maintainer of boost/bind.hpp

In boost/bind.hpp there is injection of a boost namespace contents into the global namespace: ```c++ #include <boost/bind/bind.hpp> #ifndef BOOST_BIND_NO_PLACEHOLDERS #if defined(BOOST_CLANG) # pragma clang diagnostic push # if __has_warning("-Wheader-hygiene") # pragma clang diagnostic ignored "-Wheader-hygiene" # endif #endif using namespace boost::placeholders; #if defined(BOOST_CLANG) # pragma clang diagnostic pop #endif #endif // #ifndef BOOST_BIND_NO_PLACEHOLDERS ``` The fact that Boost actually disables the relevant compiler warning makes this particularly insidious. No modern C++ library should ever do "using namespace" into the global namespace in its public headers. Please fix this in the next release of Boost. Niall