[Boost-users] [iostreams] with compression filters?

Dear boosters, I'm trying to compile IOStreams from 1.38.0 with bzip2 compression enabled on windows. The docs say "you will need to set variables indicating the location of the source files". Setting boost.build variables in user-config.jam doesn't seem to do the trick. Providing "-s|BZIP2_SOURCE|=..." or any of the other related variables or combinations thereof on the command line for bjam does not help. Does anyone out there have an example on how to do this exactly? I suggest such an example to be added to the documentation. Or is this a bug in the build system? Regards, Mikko