hgweb: Respond with HTTP 403 for disabled archive types instead of 404
This makes it easier for clients/users to distinct between supported
but disabled and unsupported archive types.
#!/bin/sh
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i