fix significant spaces after /usr

git-svn-id: https://svn.r-project.org/ESS/trunk@5954 0bbaf3bd-34e0-0310-bf65-c717079852d4
add an explicit check for debian distro before creating a simlink

git-svn-id: https://svn.r-project.org/ESS/trunk@5955 0bbaf3bd-34e0-0310-bf65-c717079852d4