[boost] [ref] incompatibility with c++0x

The latest c++0x FCD defines the single argument constructor for reference_wrapper(T &) as non-explicit. The boost version is explicit. Was it done on purpose? Should it be changed to non-explicit? BTW, I think original standard drafts did have it as explicit since gcc 4.3.3 still defines it as explicit. But in the final draft (as in gcc 4.5) it's non-explicit. I know that boost::reference_wrapper is not the same as std::reference_wrapper, but still it would be nice to have some uniformity. Thanks, Andy.