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/HACKING.md

@@ -100,9 +100,9 @@ The standard colour identifiers are:
 ```
 
 
-See Linux Journal for more information article
-<https://www.linuxjournal.com/content/programming-color-ncurses> for more
-details.
+See [Linux Journal for more information
+article](https://www.linuxjournal.com/content/programming-color-ncurses)
+for more details.
 
 
 ## Modifying the characters for the wall, bug and snake