fix compiler errors/warnings for clang 5.0

source/gui/notifier.cpp

@@ -265,6 +265,9 @@ namespace nana
 
 			auto ico = impl_->icons[impl_->play_index++];
 			impl_->set_icon(ico);
+#else
+			//eliminates warnings in clang
+			static_cast<void>(this);
 #endif
 		});