The goal of this is to make sure that all backend flows are compatible
and we can map between them, so that e.g. the aiger model can be used to
minimize a counterexample trace produced by smtbmc. Reducing the parts
that differ per backend (including parts that receive different input
depending on the used backend) also makes testing more effective as the
common parts are easier to cover.
Organize tests into subdirectories and use a new makefile that scans
.sby files and allows selecting tests by mode, engine, solver and/or
subdirectory. Automatically skips tests that use engines/solvers that
are not found in the PATH.
See `cd tests; make help` for a description of supported make targets.
