fix many internal links

Fixed a number of internal links that need to
go to the GitHub site.

Ran `make www` to perform the above.

2020/yang/index.html

@@ -383,7 +383,7 @@ Location: <a href="../../location.html#US">US</a> - <em>United States of America
 <pre><code>    ./prog [PIN] &lt; input.txt &gt; output.c</code></pre>
 <h2 id="try">Try:</h2>
 <pre><code>    ./try.sh</code></pre>
-<p>The author provided the file <a href="cppp.cc">cppp.cc</a> which can preprocess the
+<p>The author provided the file <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2020/yang/cppp.cc">cppp.cc</a> which can preprocess the
 generated output to make them more acceptable to typical compilers. To build:</p>
 <pre><code>    make cppp</code></pre>
 <p>See the author’s remarks for more details.</p>
@@ -466,7 +466,7 @@ for large files. gcc 9.2.0 and above may crash with large files.</li>
 </ul>
 <p>For people eager to encode large files, an extra utility has been packaged
 with this entry to preprocess the generated output to make them more
-acceptable to typical compilers. View the <a href="cppp.cc">cppp.cc</a> source and
+acceptable to typical compilers. View the <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2020/yang/cppp.cc">cppp.cc</a> source and
 then compile it with a c++ compiler of your choice.</p>
 <!--