[boost] [filesystem] has_branch_path()

I'm upgrading the Boost release in use at work from 1.33.1 to 1.36.0, with surprisingly few issues actually, but I am stuck on one thing. There's a function in 1.33.1, has_branch_path(), for which I cannot see the equivalent functionality in 1.36. Part of my difficulty is that the 1.33.1 header declares but does not define the function, and I cannot see where the body code is! Any suggestions would be appreciated at this point. Thanks. - Rob.