Merge branch 'kf/http-proxy-auth-methods'

New http.proxyAuthMethod configuration variable can be used to specify what authentication method to use, as a way to work around proxies that do not give error response expected by libcurl when CURLAUTH_ANY is used. Also, the codepath for proxy authentication has been taught to use credential API to store the authentication material in user's keyrings. * kf/http-proxy-auth-methods: http: use credential API to handle proxy authentication http: allow selection of proxy authentication method