PR bin/79418 - libedit sync

Since people are talking about a posix /bin/sh, It reminded me
that I need to ping people about this PR again. NetBSD made
some efforts to make sh more posix compliant, and part of that
work involved expanding libedit's capabilities.  The patches I
made excluded those posix improvements to sh, because the patch
was big enough as it was.  I just made some small changes to
adapt apps that used libedit to the new histedit.h.  Followup
changes can be made to sh after this patch lands in cvs.

Now that ipf doesnt have the tree broken, can a commiter take
a look at the patchset at http://nixil.net/libedit-patches.tar.gz

btw, I reviewed the patches the other day and did notice that a
couple of 'new' files, that the libedit patch creates, are created
in the directory that the patch command is run. I've no idea why
this happens.  So I added a README file in the patch tarball that
basically says to go to the libedit directory and run patch with -p3.