Improvments to vg_perf:
- show percentage speedup over the first Valgrind when comparing multiple
  Valgrind
- don't accept --reps < 0
- avoid div-by-zero if the runtime is measured as zero



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@5348 a5019735-40e9-0310-863c-91ae7b9d1cf9
1 file changed