- the ''changeset'' filter is now named ''Checkins for all repositories''
- if checked, the other ''repo:...'' filters are hidden and all the
repositories are shown regardless of their selection status
- if unchecked, the other ''repo:...'' filters are shown and their values
are used for filtering
This enables one to easily create a RSS feed for all the repositories without
having to list all the repositories explicitly.
Related to #8758.
