simplify ess-get-process-variable

git-svn-id: https://svn.r-project.org/ESS/trunk@5605 0bbaf3bd-34e0-0310-bf65-c717079852d4
doc correction

git-svn-id: https://svn.r-project.org/ESS/trunk@5606 0bbaf3bd-34e0-0310-bf65-c717079852d4
fix source .Last.value problem

 .. that was interfering with org-babel evaluation.

git-svn-id: https://svn.r-project.org/ESS/trunk@5607 0bbaf3bd-34e0-0310-bf65-c717079852d4