Image_ansi_colors: dithering to the 256-colour terminal palette, for a terminal without true colour (from dev 1ce461b4)

README.md

@@ -54,7 +54,7 @@ are regenerated on each release — patches cannot be merged directly.
 Report problems (or send patches) to the author; accepted changes are
 applied to the development tree and appear in a following snapshot.
 
-This snapshot was assembled from development commit `6f49f498c3c6`.
+This snapshot was assembled from development commit `1ce461b48a7d`.
 
 ## License