net::ssl::stream is canonical in examples

We no longer need to use beast::ssl_stream to improve write performance, as
Asio now linearizes scatter/gather I/O in ssl::stream:
https://github.com/chriskohlhoff/asio/commit/17637a48ccbfa2f63941d8393a7c8316a8df4a79

example/websocket/server/async-ssl/websocket_server_async_ssl.cpp

@@ -16,14 +16,13 @@
 #include "example/common/server_certificate.hpp"
 
 #include <boost/beast/core.hpp>
-#include <boost/beast/ssl.hpp>
 #include <boost/beast/websocket.hpp>
 #include <boost/beast/websocket/ssl.hpp>
-#include <boost/asio/strand.hpp>
 #include <boost/asio/dispatch.hpp>
+#include <boost/asio/ssl.hpp>
+#include <boost/asio/strand.hpp>
 #include <algorithm>
 #include <cstdlib>
-#include <functional>
 #include <iostream>
 #include <memory>
 #include <string>
@@ -49,8 +48,7 @@ fail(beast::error_code ec, char const* what)
 // Echoes back all received WebSocket messages
 class session : public std::enable_shared_from_this<session>
 {
-    websocket::stream<
-        beast::ssl_stream<beast::tcp_stream>> ws_;
+    websocket::stream<ssl::stream<beast::tcp_stream>> ws_;
     beast::flat_buffer buffer_;
 
 public:

example/websocket/server/coro-ssl/websocket_server_coro_ssl.cpp

@@ -16,16 +16,15 @@
 #include "example/common/server_certificate.hpp"
 
 #include <boost/beast/core.hpp>
-#include <boost/beast/ssl.hpp>
 #include <boost/beast/websocket.hpp>
 #include <boost/beast/websocket/ssl.hpp>
 #include <boost/asio/detached.hpp>
 #include <boost/asio/spawn.hpp>
+#include <boost/asio/ssl.hpp>
 #include <algorithm>
 #include <cstdlib>
 #include <functional>
 #include <iostream>
-#include <memory>
 #include <string>
 #include <thread>
 #include <vector>
@@ -49,8 +48,7 @@ fail(beast::error_code ec, char const* what)
 // Echoes back all received WebSocket messages
 void
 do_session(
-    websocket::stream<
-        beast::ssl_stream<beast::tcp_stream>>& ws,
+    websocket::stream<ssl::stream<beast::tcp_stream>>& ws,
     net::yield_context yield)
 {
     beast::error_code ec;
@@ -153,7 +151,7 @@ do_listen(
                 acceptor.get_executor(),
                 std::bind(
                     &do_session,
-                    websocket::stream<beast::ssl_stream<
+                    websocket::stream<ssl::stream<
                         beast::tcp_stream>>(std::move(socket), ctx),
                     std::placeholders::_1),
                     // we ignore the result of the session,

example/websocket/server/stackless-ssl/websocket_server_stackless_ssl.cpp

@@ -16,12 +16,12 @@
 #include "example/common/server_certificate.hpp"
 
 #include <boost/beast/core.hpp>
-#include <boost/beast/ssl.hpp>
 #include <boost/beast/websocket.hpp>
 #include <boost/beast/websocket/ssl.hpp>
 #include <boost/asio/coroutine.hpp>
-#include <boost/asio/strand.hpp>
 #include <boost/asio/dispatch.hpp>
+#include <boost/asio/ssl.hpp>
+#include <boost/asio/strand.hpp>
 #include <algorithm>
 #include <cstdlib>
 #include <functional>
@@ -52,7 +52,7 @@ class session
     : public boost::asio::coroutine
     , public std::enable_shared_from_this<session>
 {
-    websocket::stream<beast::ssl_stream<beast::tcp_stream>> ws_;
+    websocket::stream<ssl::stream<beast::tcp_stream>> ws_;
     beast::flat_buffer buffer_;
 
 public:

example/websocket/server/sync-ssl/websocket_server_sync_ssl.cpp

@@ -16,11 +16,10 @@
 #include "example/common/server_certificate.hpp"
 
 #include <boost/beast/core.hpp>
-#include <boost/beast/ssl.hpp>
 #include <boost/beast/websocket.hpp>
 #include <boost/beast/websocket/ssl.hpp>
 #include <boost/asio/ip/tcp.hpp>
-#include <boost/asio/ssl/stream.hpp>
+#include <boost/asio/ssl.hpp>
 #include <cstdlib>
 #include <functional>
 #include <iostream>
@@ -43,7 +42,7 @@ do_session(tcp::socket socket, ssl::context& ctx)
     try
     {
         // Construct the websocket stream around the socket
-        websocket::stream<beast::ssl_stream<tcp::socket&>> ws{socket, ctx};
+        websocket::stream<ssl::stream<tcp::socket&>> ws{socket, ctx};
 
         // Perform the SSL handshake
         ws.next_layer().handshake(ssl::stream_base::server);