Coverage tool: handle cases where a ClassCircularityError can still occur

[rliesenfeld]

There are still cases of certain (unkown) type hierarchies for which a ClassCircularityError can occur from the ClassWriter.getCommonSuperClass(type1, type2) method.

So, we need to either a) discover which cases are these and deal with them; or b) handle the error when it occurs in a way that avoids test failures (ie, simply disregarding the class for coverage), if those cases cannot be found.