Summarise all the classes, and methods, that failed in verbose mode.

Another thing that we've monkey-patched at $WORK: if you have a very large test class hierarchy, the standard "You had test failures at test 42, 365, 370..395, 1025, 1213, 1215" message is effectively useless. What we really want to know is, in this huge list of classes, which of them failed.

Hence this patch, to remember where any failures happened, and summarise them at the end.