added wxColour(RGBColor) ctor and use it insteaf of constructing wxColour from RGBColor manually in several places (replaces patch 1662064)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@44710 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/mac/carbon/colour.h

@@ -15,6 +15,8 @@
 #include "wx/object.h"
 #include "wx/string.h"
 
+struct RGBColor;
+
 // Colour
 class WXDLLEXPORT wxColour: public wxColourBase
 {
@@ -51,6 +53,10 @@ public:
 
     const WXCOLORREF& GetPixel() const { return m_pixel; };
 
+    // Mac-specific ctor and assignment operator from the native colour
+    wxColour(const RGBColor& col);
+    wxColour& operator=(const RGBColor& col);
+
 protected :
 
     // Helper function