add: spdlog and basic client code.

3rd/spdlog/details/console_globals.h

@@ -0,0 +1,28 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+#include <mutex>
+#include <spdlog/details/null_mutex.h>
+
+namespace spdlog {
+namespace details {
+
+struct console_mutex {
+    using mutex_t = std::mutex;
+    static mutex_t &mutex() {
+        static mutex_t s_mutex;
+        return s_mutex;
+    }
+};
+
+struct console_nullmutex {
+    using mutex_t = null_mutex;
+    static mutex_t &mutex() {
+        static mutex_t s_mutex;
+        return s_mutex;
+    }
+};
+}  // namespace details
+}  // namespace spdlog