check-code: check for consistent usage of the websub filter in hgweb templates The check-code tool now expects the "desc" keyword to be followed by the "websub" filter, with the following exceptions: a) It has no filters at all, e.g. a changeset description in the raw style templates or the repository description in the summary page. b) It is followed by the "firstline" filter, e.g. the first line of the changeset description is displayed as a summary or title.