Prepare 1.3.8-rc1

Prepare 1.3.8-rc1

* Prefer $PATH_PREFIX/usr/sbin/ofpath if it exists.
* yabootconfig: Add append="video=ofonly" if the running kernel
  was booted with it.  This solves user confusion when they boot an installer with an
  install-safe label, install, then reboot the new system to find the
  console display doesn't work.  This only occurs if user does not
  specify --kernel-args so it will not interfere with distro installers
  which handle this themselves.
git-archimport-id: erbenson@alaska.net--public/yaboot--devel--1.3--patch-39