After the change in r6413, CLG_(run_thread) is called a
lot more often, increasing the polling overhead to check
for a callgrind command file (created by callgrind_control
for controlling a callgrind run in an interactive way).
This reduces the calls to only be done every 5000 BBs,
which gives a similar polling frequency as before.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@6414