- Update to version 7.40.0
* added export-to-file to plotwindow
* added graph_export_image
* added .to_image to Plot
* added .caption / .xcaption / .ycaption options to Plot
* added caption / xcaption / ycaption options to Plot_object
* added snibgo's much better ImageMagick menu items
* added series_captions option to Plot_object
* support imagevec as a vips_call argument
* added system2 and system3
* added Magick.version detector
* better image cache menu item
* added hough_line and hough_circle
* removed tear-off menus, gtk+ has deprecated them