Add files to Mac build. Fix compile.

I was getting errors about a missing NotePart_Invalid when
I noticed it wasn't a part of the enum. I don't know if that
was intentional, but it was throwing the compiling off.

src/NoteDisplay.h

@@ -22,7 +22,8 @@ enum NotePart
 	NotePart_HoldTopCap,
 	NotePart_HoldBody,
 	NotePart_HoldBottomCap,
-	NUM_NotePart
+	NUM_NotePart,
+	NotePart_Invalid
 };
 
 struct NoteResource;