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.

2018/vokes/README.md

@@ -104,8 +104,7 @@ Limitations](#issues-and-limitations).
 To build:
 
 ```
-    ${CC} -o prog prog.c -std=c11 -O3 \
-        -Wall -Wextra -pedantic -Wno-missing-prototypes
+    ${CC} -o prog prog.c -std=c11 -O3 -Wall -Wextra -pedantic -Wno-missing-prototypes
 ```
 
 `-Wno-missing-prototypes` is necessary because there aren't any

2018/vokes/index.html

@@ -209,8 +209,7 @@ implementation of counting sort, which sorts each group.</p>
 Limitations</a>.</p>
 <h3 id="building">Building:</h3>
 <p>To build:</p>
-<pre><code>    ${CC} -o prog prog.c -std=c11 -O3 \
-        -Wall -Wextra -pedantic -Wno-missing-prototypes</code></pre>
+<pre><code>    ${CC} -o prog prog.c -std=c11 -O3 -Wall -Wextra -pedantic -Wno-missing-prototypes</code></pre>
 <p><code>-Wno-missing-prototypes</code> is necessary because there aren’t any
 prototypes. (They would put the program well over the size limit.)</p>
 <p>Note: The program can also be built with <code>-std=c99</code> or <code>-std=c89</code>.</p>