+ - set up a REDO property in icons/Makefile if the screenshot wants
+ to display a move halfway through an animation
+ - set up a CROP property in icons/Makefile if the icon wants to be
+ a sub-rectangle of the whole screenshot
+
+Don't forget to `git add' the new source file, the new .R file and the
+save file in `icons', the new .html file, and any other new files that
+might have been involved.