Add a couple more examples illustrating why we need vtordisps and how they work

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@222133 91177308-0d34-0410-b5e6-96231b3b80d8
Minor readability tweaks to VFTableBuilder.cpp

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@222140 91177308-0d34-0410-b5e6-96231b3b80d8