[opt-viewer] Print allocated memory per remark in opt-stats.py

If heapy is installed print the "average" in-memory remark size.  This is
estimated by dividing the total heap size by the number of unique remarks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308537 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed