add msvc logging sink

include/spdlog/sinks/msvc_sink.h

@@ -0,0 +1,50 @@
+//
+// Copyright(c) 2016 Alexander Dalshov.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+
+#pragma once
+
+#if defined(_MSC_VER)
+
+#include <spdlog/sinks/base_sink.h>
+#include <spdlog/details/null_mutex.h>
+
+#include <WinBase.h>
+
+#include <mutex>
+#include <string>
+
+namespace spdlog
+{
+namespace sinks
+{
+/*
+* MSVC sink (logging using OutputDebugStringA)
+*/
+template<class Mutex>
+class base_msvc_sink : public base_sink < Mutex >
+{
+public:
+	explicit base_msvc_sink()
+    {
+    }
+
+    void flush() override
+    {
+    }
+
+protected:
+    void _sink_it(const details::log_msg& msg) override
+    {
+		OutputDebugStringA(msg.formatted.c_str());
+    }
+};
+
+typedef base_msvc_sink<std::mutex> msvc_sink_mt;
+typedef base_msvc_sink<details::null_mutex> msvc_sink_st;
+
+}
+}
+
+#endif