working on win32 uwp! and libremidi update

include/libremidi/output_configuration.hpp

@@ -3,8 +3,6 @@
 #include <libremidi/error.hpp>
 #include <libremidi/input_configuration.hpp>
 
-#include <string>
-
 namespace libremidi
 {
 struct output_configuration
@@ -15,7 +13,7 @@ struct output_configuration
     best to set the error callback function before opening a port.
   */
   midi_error_callback on_error{};
-  midi_error_callback on_warning{};
+  midi_warning_callback on_warning{};
 
   //! Timestamp mode for the timestamps passed to schedule_message
   uint32_t timestamps : 3 = timestamp_mode::Absolute;