improve references to source code that inspired the IOCCC

Updated `faq.md` and `README.md` to point at the BSD source for the
old Bourne shell.  Mentioned the GENIX operating system for the NS
SYS16 system.  Added a note that the links are only approximations
of the BSD code that inspired the IOCCC.

sitemap.xml

@@ -15414,11 +15414,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/faq.html</loc>
-    <lastmod>2025-01-18T10:05:03+00:00</lastmod>
+    <lastmod>2025-01-18T16:34:05+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/faq.md</loc>
-    <lastmod>2025-01-18T10:05:03+00:00</lastmod>
+    <lastmod>2025-01-18T16:33:38+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/inc/index.html</loc>
@@ -15466,11 +15466,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/README.html</loc>
-    <lastmod>2025-01-18T10:05:03+00:00</lastmod>
+    <lastmod>2025-01-18T16:34:09+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/README.md</loc>
-    <lastmod>2025-01-18T10:05:03+00:00</lastmod>
+    <lastmod>2025-01-18T16:33:04+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/robots.txt</loc>