[MERGE] Automatic discovery of tests

[Robert Collins]

Robert Collins has voted reject.
Status is now: Vetoed
Comment:
for bb: there was dicussion on list. I'm personally still uncomfortable 
with this patch.

Adding to this, we've just had _exactly_ the sort of failure mode I'm 
worried about turn up in the launchpad plugin tests.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C20071106221143.47B035601E%40juju.arbash-meinel.com%3E