Create test suite

[Jelle-Nauta]

Currently there are many different combinations of settings (mode, detect) and library-properties (exported or not, defined or not, function or other symbols, etc.) and many of these probably lead to errors, e.g. through uncompilable harness code.

Proposal: create a minimal set of libraries with a comprehensive set of symbols and properties, and a test workflow to verify that autoharness works - or find bugs that can then be addressed.