The additional diagnostics are ones that were previously being
ignored, but which we seem to have been ignoring by default rather
than as a conscious choice.
For diagnostics of which we currently have *zero* instances, treat
these as errors rather than merely warnings. The intent is to
permanently lock out future regressions of things we've completely
fixed. In the future, whenever we fix the last instance of a given
warning in a given Eclipse project, we should also promote that
diagnostic to an error to keep things clean into the future.