note old Email, header formatting, improve copyright and license

For the top level and year level README.md, where email are found,
a note was added to the effect that email addresses found above are
for historical purposes only, and should not be used today.

Old references to asking for fixes, comments, when content was used,
and next contest links were replaced with a general reference to the FAQ.

Harmonized the Copyright and License and copyright dates.
Now using Creative Commons "CC BY-SA 4.0 DEED Attribution-ShareAlike 4.0
International".

The above Creative Commons will become the standard for the IOCCC.
Replaced old `png/by-sa-3.0-88x31.png` with a new ` png/by-sa.88x31.png` icon.
Updated the top level HTML files to use the license.

2019/README.md

@@ -1,9 +1,7 @@
-2016 marked the "The Twenty Sixth International Obfuscated C Code Contest"
-==========================================================================
+# 2016 marked the "The Twenty Sixth International Obfuscated C Code Contest"
 
 
-Standard IOCCC stuff
---------------------
+## Standard IOCCC stuff
 
 Look at the README.md file for the given winning entry for information
 on how to compile it and how to run the winning program.
@@ -25,8 +23,7 @@ lacking, you may need to compile using clang or gcc instead of your local
 compiler.
 
 
-Remarks on some of the winners
-------------------------------
+## Remarks on some of the winners
 
 This year's winners are impressive!
 
@@ -51,8 +48,7 @@ without blatantly reusing their code.
 ...We'll stop spouting spoilers now. Have fun exploring all the entries!
 
 
-Remarks on some of submissions that did not win
------------------------------------------------
+## Remarks on some of submissions that did not win
 
 Some entries tried to get around the size limit by submitting a data
 file that was really C code and then blindly including code in prog.c.
@@ -72,31 +68,17 @@ Some entries seemed to have a good idea, but the implementation of
 the idea was limited in scope.
 
 
-Final Comments
---------------
+## Final Comments
 
-Please feel free to send us comments and suggestions about the
-competition, this README or anything else that you would like to see in
-future contests.
+**IMPORTANT NOTE**: See [contact.html](/contact.html) for up to date contact details
+as well as details on how to provide fixes to any of the entries.
+See also [the IOCCC FAQ](/faq.html) for addition information on the IOCCC.
 
-If you use, distribute or publish these entries in some way, please drop
-us a line.  We enjoy seeing who, where and how the contest is used.
 
-If you have problems with any of the entries, AND YOU HAVE A FIX, please
-send us the fix (patch file or the entire changed file).
+# Copyright and License
 
-For the latest information on how to contact the IOCCC Judges please visit
-
->	<https://www.ioccc.org/contact.html>
-
-For news of the next contest watch:
-
->	<https://www.ioccc.org/>
-
-=-=
-
-Copyright (C) 2019, Landon Curt Noll, Simon Cooper, and Leonid A.
-Broukhis. All Rights Reserved. Permission for personal, educational
-or non-profit use is granted provided this copyright and notice are
-included in its entirety and remains unaltered.  All other uses
-must receive prior permission from the contest judges.
+Copyright (c) 2019,2023, Landon Curt Noll and Leonid A. Broukhis. All Rights Reserved.
+This work is licensed under a [Creative Commons CC BY-SA 4.0 DEED Attribution-ShareAlike
+4.0 International](https://creativecommons.org/licenses/by-sa/4.0/) license.
+If you do use this work in some form, the [IOCCC judges](/judges.html) would appreciate
+(but does not require) if you were to [send us a note about your use](/contact.html).