Investigate running tests with `-Werror` to catch deprecated functionality

[korydraughn]

This would alert us to potential issues before a release.

[d-w-moore]

I assume we don't want the warning-to-error escalation happening in the automatic test runs. May not be advisable in the short term to bomb out on warnings at least until all deprecations and build warnings are repaired - or , the change won't realistic for a 3.3.0 milestone.

[korydraughn]

We do want this for automatic test runs. However, this isn't required for a 3.3.0 release. After all, this issue is about maintenance/testing of the library.

You can always enable -Werror in your fork and work through the deprecations (if any) in the background until you're ready to present a PR.