llvm-vtabledump: Handle Itanium VTables

Add support in the vtable dumper for the Itanium ABI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221133 91177308-0d34-0410-b5e6-96231b3b80d8
Forgot to add input file for test added in r221133

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221134 91177308-0d34-0410-b5e6-96231b3b80d8