[IMP] mail: message_unread searchable field now returns a domain. This domain is...

[IMP] mail: message_unread searchable field now returns a domain. This domain is quite complex, because it bypasses limitations of the _auto_join feature used on message_ids. It should be: message_ids.read = False. However, it takes into account the one2many model, as well as to_read being a function field also searchable. Ths parsing is not capable to handle this kind of thing correctly now without using an ugly hack. Updated _search_to_read and _search_starred.

bzr revid: tde@openerp.com-20121129144253-i9e7m2kqjteq8ajr