Rearrange some #includes to keep MSVC happy

libs/canvas/canvas/xfade_curve.h

@@ -21,6 +21,7 @@
 #define __CANVAS_XFADECURVE_H__
 
 #include "canvas/visibility.h"
+#include "canvas/item.h"
 #include "canvas/curve.h"
 
 namespace ArdourCanvas {

libs/canvas/xfade_curve.cc

@@ -22,9 +22,9 @@
 #include <exception>
 #include <algorithm>
 
-#include "canvas/utils.h"
 #include "canvas/xfade_curve.h"
 #include "canvas/interpolated_curve.h"
+#include "canvas/utils.h"
 
 using namespace ArdourCanvas;
 using std::min;