[boost] [HEAD] Ambiguity with function_traits use of `detail::`

In MSVC 8.0, when using function_traits<>, the use of "detail::" is made ambiguous with fusion's "detail::" namespace. Attached diff implements a trivial fix. HTH -- Dean Michael C. Berris http://cplusplus-soup.blogspot.com/ mikhailberis AT gmail DOT com +63 928 7291459