Convert unit tests to Catch framework and fix compilation issues

[tautschnig]

We had some pre-Catch-era unit tests still lying around unmaintained and unused. Alas, they wouldn't even compile anymore. Compilation issues are now fixed and they are embedded in the Catch framework.

Fixes: #879

• Each commit message has a non-empty body, explaining why the change was made.
• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.