+ Returns the icon with the given size; if no such icon exists, returns
+ the icon with size @c wxSYS_ICON_X and @c wxSYS_ICON_Y; if no such icon
+ exists, returns the first icon in the bundle.
+
+ If size = wxDefaultSize, returns the icon with size @c wxSYS_ICON_X and
+ @c wxSYS_ICON_Y.