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
# a test for issue586
hg init a
cd a
echo a > a
hg ci -Ama
hg init ../b
cd ../b
echo b > b
hg ci -Amb
hg pull -f ../a
hg merge
hg rm -f a
hg ci -Amc
hg st -A