hgweb: use changelog for iteration Iterating through changelog is necessary to enforce filtering.

hgweb: ignore filtered revision in revnav This changeset checks that a revision is known before adding it to the navigation. This will prevent traceback on filtered repository. This changeset result in an incorrect behaviors, Navigation link may be dropped without any replacement. However this bad navigation generation is much better than a crash

hgweb: generate revnav in two phase We first generate revision to link. Then we dispatch them in before, after list. This will help filtering of unknown revision.