Add a relocation visitor to lib object. This works via caching relocated

Add a relocation visitor to lib object. This works via caching relocated
values in a map that can be passed to consumers. Add a testcase that
ensures this works for llvm-dwarfdump.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167558 91177308-0d34-0410-b5e6-96231b3b80d8