[midi dump] fix warning

git-svn-id: svn+ssh://jackaudio.org/trunk/jack@4111 0c269be4-1314-0410-8aa9-9f06e86f4224

tools/midi_dump.c

@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <unistd.h>
 #include <assert.h>
 #include <jack/jack.h>
 #include <jack/midiport.h>