Use jmarsh's direct test of CoreMIDI compatibility

configure.ac

@@ -189,15 +189,12 @@ CXXFLAGS="$CXXFLAGS -mno-ms-bitfields"
 ],[AC_MSG_RESULT([no])])
 CFLAGS="$BACKUP_CFLAGS"
 
-AC_MSG_CHECKING(if compiler suports Apple's __has_extension(blocks) required by CoreMIDI)
+AC_MSG_CHECKING(if compiler supports CoreMIDI headers)
 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
-#ifndef __has_extension
-#define __has_extension __has_feature /* Compatibility with pre-3.0 compilers. */
-#endif
-#if __has_extension(blocks)
-#endif
-]])], [AC_MSG_RESULT(yes);AC_DEFINE([C_SUPPORTS_APPLE_BLOCKS], [],
-[compiler suports Apple's __has_extension(blocks)])], AC_MSG_RESULT(no))
+#include <CoreMIDI/MIDIServices.h>
+int main(int argc, char** argv) { return 0; }
+]])], [AC_MSG_RESULT(yes);AC_DEFINE([C_SUPPORTS_COREMIDI], [],
+[compiler supports CoreMIDI headers])], AC_MSG_RESULT(no))
 
 dnl enable disable alsa and pass it's cflags to CXXFLAGS
 AC_ARG_ENABLE(alsa-midi,

src/gui/midi.cpp

@@ -68,7 +68,7 @@ MidiHandler::MidiHandler(){
 
 MidiHandler Midi_none;
 
-#if defined(MACOSX) && defined(C_SUPPORTS_APPLE_BLOCKS)
+#if defined(MACOSX) && defined(C_SUPPORTS_COREMIDI)
 
 #include "midi_coremidi.h"
 #include "midi_coreaudio.h"