Remove almost all absolute URLs for this site

In a number of cases, an absolute URL for www.ioccc.org
was replaced with a document root relative URL.

In some cases the absolute URL was removed.

Removed mirror request pages.

2019/adamovsky/hint.html

@@ -63,7 +63,7 @@ you should disregard its shape, unless you like it, and the rest is a separator
 form of a single line followed by a section signifying the function of the program,
 a block with removed shape of lambda character. Even the official IOCCC size tool
 acknowledges this: When you call <code>./iocccsize -i &lt;prog.c</code>, using the
-<a href="https://www.ioccc.org/2019/iocccsize.c">2019 version of iocccsize</a>,
+<a href="/2019/iocccsize.c">2019 version of iocccsize</a>,
 iocccsize returns <strong>955</strong>, which is the Unicode codepoint of the <strong>&#955;</strong> character.</p>
 
 <p>It might be a surprise for you that according to the IOCCC size tool the program is