* lisp/ess-tracebug.el (ess--make-busy-timer-function): redisplay to show the spinner

    Looks like in a recent emacs (force-mode-line-update) is not calling
    redisplay.

git-svn-id: https://svn.r-project.org/ESS/trunk@5964 0bbaf3bd-34e0-0310-bf65-c717079852d4