Refactor beast::asio:

* New tools for completion handlers:
  - wrap_handler provides composed io_service execution guarantees.
  - bind_handler rebinds arguments to handlers.
  - shared_handler type-erases any completion handler.
  - buffer_sequence type-erases templated BufferSequences
  - abstract_socket replaces Socket
  - socket_wrapper replaces SocketWrapper
  - beast::asio placeholders to work with std::bind

* Removed obsolete classes and functions
  - AbstractHandler
  - ComposedAsyncOperation
  - SharedFunction
  - SharedHandler
  - SharedHandlerAllocator
  - SharedHandlerPtr
  - SharedHandlerType
  - SocketBase
  - SocketWrapperStrand
  - wrapHandler

* Refactored classes to use new tools
  - abstract_socket
  - socket_wrapper
  - HandshakeDetector
  - HttpClientType

* Miscellanous tidying
  - socket classes moved to beast::asio namespace
  - beast asio files provide their own namespace declaration.
  - Fix IsCallPossible conflicting template parameter name
  - Use <boost/get_pointer.hpp> for C++11 compatibility.
  - Remove extraneous include path from build environment.

modules/beast_asio/tests/TestPeerLogicAsyncClient.cpp

@@ -17,7 +17,10 @@
 */
 //==============================================================================
 
-TestPeerLogicAsyncClient::TestPeerLogicAsyncClient (Socket& socket)
+namespace beast {
+namespace asio {
+
+TestPeerLogicAsyncClient::TestPeerLogicAsyncClient (abstract_socket& socket)
     : TestPeerLogic (socket)
 {
 }
@@ -39,7 +42,7 @@ void TestPeerLogicAsyncClient::on_connect_async (error_code const& ec)
 
     if (socket ().needs_handshake ())
     {
-        socket ().async_handshake (Socket::client,
+        socket ().async_handshake (abstract_socket::client,
             boost::bind (&TestPeerLogicAsyncClient::on_handshake, this,
             boost::asio::placeholders::error));
     }
@@ -108,7 +111,7 @@ void TestPeerLogicAsyncClient::on_read_final (error_code const& ec, std::size_t)
         {
             // on_shutdown will call finished ()
             error_code ec;
-            on_shutdown (socket ().shutdown (Socket::shutdown_send, ec));
+            on_shutdown (socket ().shutdown (abstract_socket::shutdown_send, ec));
         }
     }
     else
@@ -137,7 +140,7 @@ void TestPeerLogicAsyncClient::on_shutdown (error_code const& ec)
         {
             if (socket ().needs_handshake ())
             {
-                socket ().shutdown (Socket::shutdown_send, error ());
+                socket ().shutdown (abstract_socket::shutdown_send, error ());
             }
 
             if (! error ())
@@ -153,3 +156,6 @@ void TestPeerLogicAsyncClient::on_shutdown (error_code const& ec)
 
     finished ();
 }
+
+}
+}