Mercurial version on hgweb & IIS

[Anton Shestakov]

Due to a decision from a long time ago, there's no version string
anywhere in hgweb. But you can find something in
https://www.mercurial-scm.org/wiki/WhatsNew that's supposed to work
only in newly upgraded version and check if it works. For 4.1 it would
be Content Security Policy, so you can navigate to
reponame/help/config and see if there's "csp" option in "web" section.