libremidi update to v5.4.3 and added virtual midi out as default

include/libremidi/backends/emscripten/midi_in.hpp

@@ -4,7 +4,7 @@
 #include <libremidi/detail/midi_in.hpp>
 #include <libremidi/detail/midi_stream_decoder.hpp>
 
-namespace libremidi
+NAMESPACE_LIBREMIDI
 {
 class midi_in_emscripten final
     : public midi1::in_api
@@ -31,7 +31,7 @@ public:
   void on_input(double ts, unsigned char* begin, unsigned char* end);
 
 private:
-  int portNumber_{};
+  int m_portNumber{};
 
   midi1::input_state_machine m_processing{this->configuration};
 };