[boost] Where is boost/detail/limits.hpp used?

I'm playing with a dependency checker I wrote that tells me what Boost module depends on what. Starting with the basics: Dependencies for config: detail: boost/detail/endian.hpp A dependency from config to detail is not a good thing because detail depends on too much. boost/detail/endian.hpp is now only a forwarding header to predef, so it could and probably should be moved to predef, which seems to depend on nothing. But I was wondering what in config uses endian.hpp. Turns out the only use is in boost/detail/limits.hpp, a file that has been put into config for some reason. I can't find anything in config or in Boost that uses this file. What is its purpose?