Please change the url written in named-readtables/source.txt from
http://common-lisp.net/project/editor-hints/darcs/named-readtables/ to
https://github.com/kmizumar/named-readtables
Allegro CL 8.2 and later requires a slight change to load named-readtables:
kmizumar/named-readtables@d4d41e9
But Tobias C. Rittweiler (the original author) discontinues maintenance.
If you have any other good idea, please let me know.