tracebug cosmetic

git-svn-id: https://svn.r-project.org/ESS/trunk@5460 0bbaf3bd-34e0-0310-bf65-c717079852d4
don't run comint hooks twice

git-svn-id: https://svn.r-project.org/ESS/trunk@5461 0bbaf3bd-34e0-0310-bf65-c717079852d4
replace exponential waiting with threshold waiting in ess-wait-for-process

git-svn-id: https://svn.r-project.org/ESS/trunk@5462 0bbaf3bd-34e0-0310-bf65-c717079852d4