fix links in entry HTML files other than index.html

Fixed internal links in entry HTML files other than index.html.

Removed links to markdown files that otherwise used to
generate HTML files other than index.html.

Ran `make gen_other_html` to perform the above.

2020/ferguson1/COMPILING.html

@@ -139,7 +139,8 @@ C99+ and ncurses; note that for some platforms (e.g. Red Hat based Linux) you
 will need two different packages: the library itself but also the dev package
 that has the header files etc. If you use the Makefile obviously you need <code>make</code>
 too.</p>
-<p>In <a href="gameplay.md">gameplay.md</a> I show how to easily customise the colours, set up
+<p>In <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2020/ferguson1/gameplay.html">gameplay.html</a>
+I show how to easily customise the colours, set up
 different gameplay modes and various other things. The troubleshooting.md
 and terminals.md as well as bugs.md include a variety of information
 should you run into trouble.</p>
@@ -162,7 +163,7 @@ matters; I only have Intel CPUs and arm64 (MacBook Pro M1).</p>
 <p>You don’t need Xcode itself and it appears that the command line tools (as above
 should install) already has ncurses so there shouldn’t be anything else that
 needs to be done. But I’m not actually sure of this - I’m seeing conflicting
-information and it’s been too long; anyway there’s always <a href="https://www.macports.org">MacPorts</a> and also
+information and it’s been too long; anyway there’s always [MacPorts][] and also
 Homebrew which should be sufficient; I do <em>NOT</em> recommend Homebrew however:
 it takes ownership of /usr/local: as in the user you run it as is the new owner
 so that you don’t need sudo because … Well never mind.</p>