Add wxCursor ctor from XPM data to all ports

This just uses the existing wxImage ctor from XPM data and wxCursor ctor
from wxImage, but will allow the code creating cursors from XPM to still
work even when wxImage ctor from XPM is made explicit.

Add a trivial test just to check that the new ctor can be used.

include/wx/dfb/cursor.h

@@ -11,6 +11,7 @@
 #define _WX_DFB_CURSOR_H_
 
 class WXDLLIMPEXP_FWD_CORE wxBitmap;
+class WXDLLIMPEXP_FWD_CORE wxImage;
 
 //-----------------------------------------------------------------------------
 // wxCursor
@@ -24,6 +25,10 @@ public:
 #if WXWIN_COMPATIBILITY_2_8
     wxCursor(int id) { InitFromStock((wxStockCursor)id); }
 #endif
+#if wxUSE_IMAGE
+    wxCursor(const wxImage& image);
+    wxCursor(const char* const* xpmData);
+#endif // wxUSE_IMAGE
     wxCursor(const wxString& name,
              wxBitmapType type = wxCURSOR_DEFAULT_TYPE,
              int hotSpotX = 0, int hotSpotY = 0);