Update the petitboot package to the latest version
in the petitboot git repo.
Add new build config options to allow selection of which of
the petitboot user interface program to run at system boot.
git-svn-id: svn://svn.openwrt.org/openwrt/packages@16762 3c298f89-4303-0410-b956-a3cf2f4a3e73