add a consistent set of text about X11

1994/tvr/README.md

@@ -4,6 +4,9 @@
     make all
 ```
 
+NOTE: this entry requires the `X11/Xlib.h` header file and the X11 library to
+compile.  For more information see the
+FAQ on "[X11](../../faq.html#X11)".
 
 The author provided a less obfuscated version as alternate code. See [Alternate
 code](#alternate-code) below.

1994/tvr/index.html

@@ -409,6 +409,9 @@ Location: <a href="../../location.html#FI">FI</a> - <em>Republic of Finland </em
 <!-- BEFORE: 1st line of markdown file: 1994/tvr/README.md -->
 <h2 id="to-build">To build:</h2>
 <pre><code>    make all</code></pre>
+<p>NOTE: this entry requires the <code>X11/Xlib.h</code> header file and the X11 library to
+compile. For more information see the
+FAQ on “<a href="../../faq.html#X11">X11</a>”.</p>
 <p>The author provided a less obfuscated version as alternate code. See <a href="#alternate-code">Alternate
 code</a> below.</p>
 <h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>