Merge branch 'deeringc-master' into development

Author: kavyako

CONTRIBUTORS.txt

@@ -34,6 +34,7 @@ Gery Vessere (gery@vessere.com)
 
 Cisco Systems
 Gergely Lukacsy (glukacsy)
+Chris Deering (deeringc)
 
 Ocedo GmbH
 Henning Pfeiffer (megaposer)

Release/include/cpprest/details/web_utilities.h

@@ -30,6 +30,7 @@ namespace web
 namespace http { namespace client { namespace details {
 class winhttp_client;
 class winrt_client;
+class asio_context;
 }}}
 namespace websockets { namespace client { namespace details {
 class winrt_callback_client;
@@ -124,6 +125,7 @@ class credentials
 private:
     friend class http::client::details::winhttp_client;
     friend class http::client::details::winrt_client;
+	friend class http::client::details::asio_context;
     friend class websockets::client::details::winrt_callback_client;
     friend class websockets::client::details::wspp_callback_client;