Moved all Win16 definitions out of the standard Windows headers.

diff --git a/include/mmddk.h b/include/mmddk.h
index b08cdac..7509fc8 100644
--- a/include/mmddk.h
+++ b/include/mmddk.h
@@ -15,6 +15,7 @@
 
 #include "mmsystem.h"
 #include "winbase.h"
+#include "wine/mmsystem16.h"
 
 #define MAX_MIDIINDRV 	(16)
 /* For now I'm making 16 the maximum number of midi devices one can