Dont allow including of dup_filter_sink if SPDLOG_NO_DATETIME is defined

include/spdlog/sinks/dup_filter_sink.h

@@ -33,6 +33,11 @@
 //       [2019-06-25 17:50:56.512] [logger] [info] Skipped 3 duplicate messages..
 //       [2019-06-25 17:50:56.512] [logger] [info] Different Hello
 
+
+#ifdef SPDLOG_NO_DATETIME
+#error "spdlog::sinks::dup_filter_sink: cannot work when SPDLOG_NO_DATETIME is defined"
+#endif
+
 namespace spdlog {
 namespace sinks {
 template<typename Mutex>