_update-info-dir (was: libXm.so)

Hello,

I was skimming this thread, and found an answer to a question I did have time to make:

Dave Korn wrote:

  http://cygwin.com/packages/ is the best place to search.  If it's in the
cygwin distro, that will tell you which package you need installed.

But what I am looking for is:
 _update-info-dir/_update-info-dir-00573-1       Generate info/dir file automatically

Now, trying to install this from setup, I cannot find it.
I assume it should be in the Doc category, but is not.
I cycle the View to show all packages, and get the full list in alphabetic order, from
 a2ps
to
 zsh

If the leading '_' was ignored, it ought to be between unzip and upx...

What am I missing?

Thanks,
Marc