julia: add ac-help

git-svn-id: https://svn.r-project.org/ESS/trunk@5734 0bbaf3bd-34e0-0310-bf65-c717079852d4
julia: change help command

git-svn-id: https://svn.r-project.org/ESS/trunk@5735 0bbaf3bd-34e0-0310-bf65-c717079852d4