use default move constructor/assignment for async_log_helper

include/spdlog/details/async_log_helper.h

@@ -52,28 +52,13 @@ class async_log_helper
 
         async_msg() = default;
         ~async_msg() = default;
-
-async_msg(async_msg&& other) SPDLOG_NOEXCEPT:
-        logger_name(std::move(other.logger_name)),
-                    level(std::move(other.level)),
-                    time(std::move(other.time)),
-                    txt(std::move(other.txt)),
-                    msg_type(std::move(other.msg_type))
-        {}
+        async_msg(async_msg&& ) = default;
 
         async_msg(async_msg_type m_type) :msg_type(m_type)
         {};
 
-        async_msg& operator=(async_msg&& other) SPDLOG_NOEXCEPT
-        {
-            logger_name = std::move(other.logger_name);
-            level = other.level;
-            time = std::move(other.time);
-            thread_id = other.thread_id;
-            txt = std::move(other.txt);
-            msg_type = other.msg_type;
-            return *this;
-        }
+        async_msg& operator=(async_msg&& ) = default;
+
         // never copy or assign. should only be moved..
         async_msg(const async_msg&) = delete;
         async_msg& operator=(async_msg& other) = delete;