Added support for the BIT type

- Moved socket_connection to a separate include file.
- Clarified Stream requirements.
- Made make_error_code public.
- Updated include styles to match Boost's.
- Moved <boost/myql/mysql.hpp> to <boost/mysql.hpp> to match
conventions.
- Added support for the BIT type.

closes #13
closes #21

test/unit/socket_connection.cpp

@@ -0,0 +1,28 @@
+//
+// Copyright (c) 2019-2021 Ruben Perez Hidalgo (rubenperez038 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)
+//
+
+#include <boost/mysql/socket_connection.hpp>
+#include <boost/asio/strand.hpp>
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_SUITE(test_socket_connection)
+
+using other_executor = boost::asio::strand<boost::asio::io_context::executor_type>;
+
+BOOST_AUTO_TEST_CASE(socket_connection_rebind_executor)
+{
+    using rebound_type = boost::mysql::tcp_connection::rebind_executor<other_executor>::other;
+    using expected_type = boost::mysql::socket_connection<
+        boost::asio::basic_stream_socket<
+            boost::asio::ip::tcp,
+            other_executor
+        >
+    >;
+    BOOST_TEST((std::is_same<rebound_type, expected_type>::value));
+}
+
+BOOST_AUTO_TEST_SUITE_END() // test_socket_connection