Gets the stock icon name and size being displayed by the gtk.Image
The storage type of the image must be GTK_IMAGE_EMPTY or
GTK_IMAGE_STOCK (see Image.getStorageType).
The returned string is owned by the gtk.Image and should not
place to store a
stock icon name, or NULL
place to store a stock icon
size (gtk.IconSize), or NULL
Deprecated: Use Image.getIconName instead.