This documentation had been previously removed in 1999 in [1]
but was subsequently restored again in a different form in 2006
in [2] as the construct was still supported on some systems.
However it looks like it hasn't done what that documentation
indicated since [3] in 2011, and the final remnant of this
functionality was removed in [4] in 2013; so it seems clear that
it's no longer supported and shouldn't be documented now.