[DebugInfo] Put the vftable index in the debug info

This won't always be enough info to call a virtual method from the
debugger, but it's a start.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@272944 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed