This:
- Removes the reportUniqueWarning overload that accepts Error Err.
We can live with the version that accepts const Twine & and
anyways warnings reported in many places touched by this patch can probably
be improved. To do that we would need to use Twine version anyways.
- Converts the last reportWarning in ELFDumper.cpp to reportUniqueWarning.
In that place it is a no-op I believe.