rewrite bin/tar-entry.sh

We rewrote the `bin/tar-entry.sh` algorithm so that we do NOT have
to require Linux to produce a compressed tarball that is byte-for-byte
identical to a macOS compressed tarball for the same entry.

Changed `bin/tar-entry.sh` VERSION from "1.2 2024-03-22"
to "1.3 2024-03-25".

Added `bin/untar-entry.sh` to untar an entry from the
compressed tarball.

Added `make untar_entry_tarball` to untar all entry files.

Added `make untar_year_tarball` and `make untar_all_tarball`
stub Makefile rules.  The core it referred to does not yet exist.

Updated IOCCC manifest.  Updated `.entry.json` for `2004/sds`.

Performed `make www` to update web pages.  In most cases the
entry `index.html` added an inventory link for the new `.tar.tstamp` file.

Performed `form_entry_tarball` to complete the test of the above.

TODO: Test the results under Linux.

TODO: Update `bin/tar-year.sh`.  Update year level compressed tarballs.

TODO: Update `bin/tar-all.sh`.  Update top level compressed tarball.

TODO: Write `bin/untar-year.sh` and `bin/untar-all.sh`.

1991/cdupont/index.html

@@ -196,6 +196,7 @@ you to place the meaningful letters wherever you want.</p>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1991/cdupont/.entry.json">.entry.json</a> - description of entry in JSON</li>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1991/cdupont/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
 <li><a href=".path">.path</a> - directory path from top directory</li>
+<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1991/cdupont/.tar.tstamp">.tar.tstamp</a> - timestamp of compressed tarball formation</li>
 </ul>
 
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