fix mirror lub equality assertion
add pend to test depending on undefined constant
add tmp dir to ignored files
move debugging help to the test helper

turns out that other tests could benefit from being able to do finer logging
break out failing superclass type update mirror test
add toString to NarrowingTypeFuture
move local var def in mirrors base_type closer to usage
fix superclass mirror type updates

mirror superclass definition changes were not being propagated because the resolved type was staying the same due to the earlier change I added where MirrorProxies now proxy equals. Now the mirror type explicitly tells the TypeFuture to forget its previous type when updating that type, forcing all listeners to be updated.