[boost] [disjoint_sets] 1.49.0 docs out-of-date? pending?

I noticed that http://www.boost.org/doc/libs/1_49_0/libs/disjoint_sets/disjoint_sets.html references boost/disjoint_sets.hpp but, AFAICS, no such file exists; however, clicking on the file nonetheless redirects to boost/pending/disjoint_sets.hpp which presumably is the intended reference. So, aside from what looks like a slight error in the present disjoint_sets docs, what is the purpose of this pending directory? I had never noticed it before and I don't remember stumbling upon a reference to it until now. Looks like it contains a hodgepodge of miscellaneous headers... Thanks, - Jeff