Add async-ssl-system-executor http client example

This example websocket client application uses the `system_executor` to show
how to use it with the I/O objects in ASIO and Beast.

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>

example/websocket/client/async-ssl-system-executor/Jamfile

@@ -0,0 +1,22 @@
+#
+# Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
+#
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+#
+# Official repository: https://github.com/boostorg/beast
+#
+
+import ac ;
+
+project
+    : requirements
+        [ ac.check-library /boost/beast//lib-asio-ssl : <library>/boost/beast//lib-asio-ssl/<link>static : <build>no ]
+    ;
+
+exe websocket-client-async-ssl-system-executor :
+    websocket_client_async_ssl_system_executor.cpp
+    :
+    <variant>coverage:<build>no
+    <variant>ubasan:<build>no
+    ;