[Bug-cpio] divulge fate of access times

[Dan Jacobson]

In the Info page near

`-m, --preserve-modification-time'
     Retain previous file modification times when creating files.

why don't you mention what you do about _access_ times upon reading
and writing? Apparently on -im you set them to the modification time,
for lack of anything better to do. OK, then at least be up front about
this somewhere in the manual. Mention "or else when making the archive
we must stat each file more and use extra data structures" or
something.

The tar man page mentions access times.