Deprecate twitter

We further deprecate the use of twitter.

In cases such as historic guidelines and rules, we add
a note about using Mastodon.

In cases where a tweet URL was used, we replace with
an Internet Archive link because twitter has announced
that accounts that are not used for a period of time
will be deleted.

We add a few missing deprecated_twitter information
to the author.numbers and author.cvs files.

We remove references to twitter handles (after making
sure that both author.numbers and author.cvs has the
deprecated_twitter information).  When the "_README.md_"
files have their header information generated by
a tool, such deprecated_twitter data will not be present.

2015/rules.txt

@@ -257,6 +257,17 @@ FOR MORE INFORMATION:
     Non-twitter users should force their browsers to reload the above URL
     to be sure they are seeing the most recent tweets.
 
+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+An important 2023 update to this historic note:
+
+The IOCCC no longer uses twitter.  Today the IOCCC uses Mastodon.
+For more information and to see our IOCCC Mastodon posts, see:
+
+    https://fosstodon.org/@ioccc
+
+End of important 2023 update to this historic note.
+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
 Leonid A. Broukhis
 Simon Cooper
 chongo (Landon Curt Noll) /\cc/\