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/kurdyukov4/README.md

@@ -30,7 +30,7 @@ context length decreases:
 
 ## Judges' remarks:
 
-We were able to [write our own program](rand.c) performing the same trick using
+We were able to [write our own program](%%REPO_URL%%/2020/kurdyukov4/rand.c) performing the same trick using
 the (still non-standard, for some reason) library function `memmem()`, but that
 way it works too fast regardless of the context length, and it's much less fun.
 

2020/kurdyukov4/index.html

@@ -389,7 +389,7 @@ context length decreases:</p>
     Too many identical strings if the context length is small.
     -- Author</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
-<p>We were able to <a href="rand.c">write our own program</a> performing the same trick using
+<p>We were able to <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2020/kurdyukov4/rand.c">write our own program</a> performing the same trick using
 the (still non-standard, for some reason) library function <code>memmem()</code>, but that
 way it works too fast regardless of the context length, and it’s much less fun.</p>
 <p>The author wrote in reply:</p>