split spdlog.cpp to multiple .cpp files

src/async.cpp

@@ -0,0 +1,12 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#ifndef SPDLOG_COMPILED_LIB
+#error Please define SPDLOG_COMPILED_LIB to compile this file.
+#endif
+
+#include "spdlog/async.h"
+#include "spdlog/async_logger-inl.h"
+#include "spdlog/details/periodic_worker-inl.h"
+#include "spdlog/details/thread_pool-inl.h"
+template class spdlog::details::mpmc_blocking_queue<spdlog::details::async_msg>;