fix HTML problems related to pandoc and markdown image notation

Improve `make clobber` for `2004/anonymous`.

Instead of using this markdown element to embed an image:

```
![alt text](filename.png "Title")
```

Use a "img" HTML element with "alt", "alt", "width" and "length"
attributes:

```
<img src="filename.png"
 alt="describe the filename.png image for someone who cannot view it"
 width=PIXEL_WIDTH height=PIXEL_HEIGHT>
```

This was performed for:

```
2004/anonymous/index.html
2005/boutines/index.html
2011/goren/index.html
2012/vik/index.html
2013/birken/index.html
2013/cable1/index.html
2013/cable3/index.html
2013/hou/doc/example.html
2013/hou/index.html
2020/ferguson1/chocolate-cake.html
```

In the case of `2013/cable1/index.html` we reduce the displayed
image size by a factor for 2.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

In the case of `2013/hou/index.html` we reduce the displayed
image size by a factor for 2.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

In the case of `2020/ferguson1/chocolate-cake.html` we reduce the displayed
image size by a factor for 4.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

Run `make www` to perform the above.

2012/vik/README.md

@@ -83,10 +83,11 @@ Use `vik.alt` as you would `vik` above.
 References to chocolate had no effect on judging this entry. We
 guarantee it.
 
-Can you discern hidden pieces of chocolate in
-[chocolate-in-ioccc.png](chocolate-in-ioccc.png)?
+Can you discern hidden pieces of chocolate in:
 
-![chocolate in ioccc](chocolate-in-ioccc.png "Chocolate in IOCCC")
+<img src="chocolate.png"
+ alt="image of peices of chocolate candy"
+ width=300 height=110>
 
 
 ## Author's remarks:

2012/vik/index.html

@@ -183,12 +183,10 @@ code</a> section below.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>References to chocolate had no effect on judging this entry. We
 guarantee it.</p>
-<p>Can you discern hidden pieces of chocolate in
-<a href="chocolate-in-ioccc.png">chocolate-in-ioccc.png</a>?</p>
-<figure>
-<img src="chocolate-in-ioccc.png" title="Chocolate in IOCCC" alt="chocolate in ioccc" />
-<figcaption aria-hidden="true">chocolate in ioccc</figcaption>
-</figure>
+<p>Can you discern hidden pieces of chocolate in:</p>
+<p><img src="chocolate.png"
+ alt="image of peices of chocolate candy"
+ width=300 height=110></p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="introduction">Introduction</h3>
 <p>This program is a <a href="https://en.wikipedia.org/wiki/Steganography">steganography</a>