directory is not contained in OpenBSD base, and because even people
having the directory often don't understand that they need to run
makewhatis(8) - and instead complain about the resulting warnings.
This commit reverts revisions 1.17 and 1.21.
Requested by deraadt@ millert@ kettenis@ who argue that people
using /usr/ports/infrastructure/bin/ already need to set PATH,
so editing man.conf (or, though more fragile, setting MANPATH)
should not be a big deal for them.