more double promote fixes, still not complete

rtengine/color.h

@@ -20,16 +20,16 @@
 #pragma once
 
 #include <array>
-#include <glibmm/ustring.h>
 
 #include "rt_math.h"
 #include "LUT.h"
-#include "iccmatrices.h"
 #include "lcms2.h"
 #include "sleef.h"
 
-#define SAT(a,b,c) ((float)max(a,b,c)-(float)min(a,b,c))/(float)max(a,b,c)
-
+namespace Glib
+{
+class ustring;
+}
 namespace rtengine
 {