Performance measure R code with many of Ross Bennett's suggestions

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/uwgarp@110 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
git-svn-id: svn://svn.r-forge.r-project.org/svnroot/uwgarp@111 edb9625f-4e0d-4859-8d74-9fd3b1da38cb