hgweb/templates: remove unused vars from map-raw
annotateline contains html and it is unused
filenodelink is unused but should be defined
Fall back to asciidoc6 html backend if html4 doesn't work.
This reenables building documentation on Debian sarge,
which broke after
9346a7fb3fe2.
Reverted name change (mercurial -> Mercurial) from
dd5085897010.