refactor user variables from -dbg- into -debug-

git-svn-id: https://svn.r-project.org/ESS/trunk@5533 0bbaf3bd-34e0-0310-bf65-c717079852d4
idem

git-svn-id: https://svn.r-project.org/ESS/trunk@5534 0bbaf3bd-34e0-0310-bf65-c717079852d4
idem

git-svn-id: https://svn.r-project.org/ESS/trunk@5535 0bbaf3bd-34e0-0310-bf65-c717079852d4