fix problematic HTML caused by certain trailing backslashes

In cases that are **outside of a markdown code block**,
a markdown line with ending in a tailing "\" can generate
problematic HTML.

We certain trailing backslashes outside of a markdown code block
with "<br>" HTML elements, or in some cases eliminated the
need for a trailing backslash.

In a few cases some unnecessary trailing backslashes inside
of a markdown code block were removed.

The following markdown files were changed in this commit:

```
1990/dds/README.md
1990/jaw/README.md
1991/ant/README.md
1991/rince/README.md
1991/westley/README.md
1992/vern/README.md
1992/westley/README.md
1998/schweikh1/README.md
2004/anonymous/README.md
2005/sykes/README.md
2006/toledo2/README.md
2011/toledo/README.md
2012/endoh2/README.md
2012/tromp/README.md
2013/robison/README.md
2015/hou/README.md
2015/howe/README.md
2015/schweikhardt/README.md
2018/burton1/README.md
2018/burton2/README.md
2018/ferguson/README.md
2018/vokes/README.md
2020/ferguson1/README.md
```

Performed `make www` to test these changes.

2005/sykes/README.md

@@ -154,9 +154,14 @@ Supplied also is a short demo program written in
 ```
 
 Many other old programs will run in this emulator too. Files with a `.PRG`
-extension should work. (Look, for instance, here:
-<http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html>,\
-or try this one: <http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg>)\
+extension should work.  Look, for instance, here:
+
+[http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html](http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html)
+
+or try this one:
+
+[http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg](http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg)
+
 The filenames must be upper case in order to be loaded by the emulator.
 
 You can save programs too - try

2005/sykes/index.html

@@ -231,10 +231,11 @@ slower cursor blink, try</p>
 <pre><code>    LOAD &quot;DEMO&quot;
     RUN</code></pre>
 <p>Many other old programs will run in this emulator too. Files with a <code>.PRG</code>
-extension should work. (Look, for instance, here:
-<a href="http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html" class="uri">http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html</a>,<br />
-or try this one: <a href="http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg" class="uri">http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg</a>)<br />
-The filenames must be upper case in order to be loaded by the emulator.</p>
+extension should work. Look, for instance, here:</p>
+<p><a href="http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html">http://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html</a></p>
+<p>or try this one:</p>
+<p><a href="http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg">http://www.zimmers.net/anonftp/pub/cbm/pet/games/english/dungeon.prg</a></p>
+<p>The filenames must be upper case in order to be loaded by the emulator.</p>
 <p>You can save programs too - try</p>
 <pre><code>    10 PRINT &quot;HELLO!&quot;
     SAVE &quot;HELLO&quot;