Add eventlog_sink for logging to Windows Event Log (local only).

tests/CMakeLists.txt

@@ -12,6 +12,7 @@ set(SPDLOG_UTESTS_SOURCES
     test_file_logging.cpp
 	test_daily_logger.cpp
     test_misc.cpp
+    test_eventlog.cpp
     test_pattern_formatter.cpp
     test_async.cpp
     test_registry.cpp