/usr/include/boost/config/platform/ is in libboost1.46-dev 1.46.1-7ubuntu3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/boost/config/platform/aix.hpp
/usr/include/boost/config/platform/amigaos.hpp
/usr/include/boost/config/platform/beos.hpp
/usr/include/boost/config/platform/bsd.hpp
/usr/include/boost/config/platform/cygwin.hpp
/usr/include/boost/config/platform/hpux.hpp
/usr/include/boost/config/platform/irix.hpp
/usr/include/boost/config/platform/linux.hpp
/usr/include/boost/config/platform/macos.hpp
/usr/include/boost/config/platform/qnxnto.hpp
/usr/include/boost/config/platform/solaris.hpp
/usr/include/boost/config/platform/symbian.hpp
/usr/include/boost/config/platform/vms.hpp
/usr/include/boost/config/platform/vxworks.hpp
/usr/include/boost/config/platform/win32.hpp