allow for year level archive of rules and guidelines

Adjusted `bin/md2html.cfg` to allow for the creation of year level
archive of the rules and guidelines that were in effect when the given
year's content opened for submissions.

We improved `bin/gen-year-index.sh` so that if there exists
a `YYYY/rules.md` rules archive, then `YYYY/rules.html`
will be created.

We improved `bin/gen-year-index.sh` so that if there exists
a `YYYY/guidelines.md` rules archive, then `YYYY/guidelines.html`
will be created.

Changed `bin/gen-year-index.sh` VERSION from "2.0.0 2025-03-13"
to "2.1.0 2025-07-05".

Adjusted `next/rules.md` and `next/guidelines.md` so that when they are
copied as archived copies of rules and guidelines under a YYYY directory,
the internal links do not break.  There are **NO** changes to the readable
contents of the rules and guidelines, only some changes to a few internal links.

Updated `1992/buzzard.2/index.html, `1993/rince/index.html`, and
`2012/omoikane/index.html that were modified by recent commits.

Rebuild sitemap due to the changes above.

Ran `make www` to test and perform the above.

next/rules.html

@@ -517,9 +517,9 @@ FAQ on “<a href="../faq.html#mkiocccentry">obtaining and compiling the mkioccc
 and the
 FAQ on “<a href="../quick-start.html#enter">how to enter the IOCCC</a>”
 as that FAQ has important details on
-<a href="register.html">how to register</a>
+<a href="../next/register.html">how to register</a>
 as well as
-<a href="submit.html">how to upload your submission</a> to the IOCCC.
+<a href="../next/submit.html">how to upload your submission</a> to the IOCCC.
 </p>
 <p>Jump to: <a href="#">top</a></p>
 <div id="rules">
@@ -647,8 +647,8 @@ See also <a href="#rule17">Rule 17</a>.
 <h2 id="rule-3">Rule 3</h2>
 </div>
 <p class="leftbar">
-You must <a href="register.html">register</a> in order to submit your entry to the IOCCC.
-You may <a href="register.html">register</a> while the contest is either
+You must <a href="../next/register.html">register</a> in order to submit your entry to the IOCCC.
+You may <a href="../next/register.html">register</a> while the contest is either
 <strong><a href="../faq.html#pending">pending</a></strong> or <strong><a href="../faq.html#open">open</a></strong>.
 </p>
 <p class="leftbar">
@@ -658,14 +658,14 @@ will email you your <a href="https://submit.ioccc.org">submit server</a>
 perhaps as much as a few days, for your registration to be processed and for that email to be sent.
 </p>
 <p class="leftbar">
-Those who <a href="register.html">register</a> while the contest status is <strong><a href="../faq.html#pending">pending</a></strong>
+Those who <a href="../next/register.html">register</a> while the contest status is <strong><a href="../faq.html#pending">pending</a></strong>
 will receive their email (containing their <a href="https://submit.ioccc.org">submit server</a> <strong>Username</strong>
 and <strong>Initial password</strong>), later: usually a few days around the time when the contest status
 becomes <strong><a href="../faq.html#open">open</a></strong>.
 </p>
 <p class="leftbar">
 Once that email with your <strong>Username</strong> and <strong>Initial password</strong> is sent, you
-will have fortnight (<strong>14 days</strong>) to <a href="pw-change.html">change your submit server initial password</a>.
+will have fortnight (<strong>14 days</strong>) to <a href="../next/pw-change.html">change your submit server initial password</a>.
 </p>
 <p class="leftbar">
 If you do not change your <strong>Initial password</strong> in time, you will have to
@@ -803,7 +803,7 @@ Submissions may only be uploaded to the <a href="https://submit.ioccc.org">IOCCC
 while the contest is <strong><a href="../faq.html#open">open</a></strong>.
 </p>
 <p class="leftbar">
-If you have <a href="register.html">registered</a> and received by email your <a href="https://submit.ioccc.org">submit
+If you have <a href="../next/register.html">registered</a> and received by email your <a href="https://submit.ioccc.org">submit
 server</a> <strong>Username</strong> and <strong>Initial password</strong> you may
 upload your submission to the <a href="https://submit.ioccc.org">submit server</a> but
 <strong>ONLY</strong> while the contest is <strong><a href="../faq.html#open">open</a></strong>.
@@ -1266,9 +1266,9 @@ FAQ on “<a href="../faq.html#mkiocccentry">obtaining, compiling, installing an
 and the
 FAQ on “<a href="../quick-start.html#enter">how to enter the IOCCC</a>”
 as that FAQ has important details on
-<a href="register.html">how to register</a>
+<a href="../next/register.html">how to register</a>
 as well as
-<a href="submit.html">how to upload your submission</a> for the IOCCC.
+<a href="../next/submit.html">how to upload your submission</a> for the IOCCC.
 </p>
 <p>Jump to: <a href="#">top</a></p>
 <p><strong>Leonid A. Broukhis</strong><br>