httpclient: update to revision 9517a2b56fe9 of httpplus (issue3905) Includes upstream change "socketutil: force SSLv3 by default, as it is safer" which should fix issue 3905.

hgweb: force connection close on early response Not all WSGI servers close the socket when an early response is sent to a large POST request, which can cause the server to interpret the already-sent request body as an incoming (but hopelessly invalid) request.

hgweb: fix incorrect revisions count in graph (issue3977) Actual amount of revisions is used now instead of their numbers in the repo before to deal with skipped numbers correctly.