Auto watch of VCS buildout itself

[Georges Racinet]

This is much simpler that #1059160:

if a buildout is specified as a VCS address, then that address must be automatically added to the watched repositories.
Example use case:

Together with inherit, this makes setups where each developer gets his own buildout column in buildbot really easy to maintain, the only expected difference being precisely in the buildout location.

[Georges Racinet (gracinet)]

This is reported not to work in reality. There are problems in Anybox's public buildbot (on the buildout recipe tests), and this is reported by S. Bidoul, too.

For now this is a bit mysterious, since it works perfectly in unit tests: the buildout repos are included correctly in the change filters.

Now that could be an inconsistency between change filters and change sources, we'll see

[Georges Racinet (gracinet)]

Added a useful log line. Example:

Scheduler 'recipe-61-latest' is for builders ['recipe-61-latest-postgresql-9.1'] with PollerChangeFilter({'http://bazaar.launchpad.net/~anybox/anybox.recipe.openerp/trunk': ('bzr', ())})