improve FAQ 5.6, thank Cody for finding broken links

The question for FAQ 5.6 was improved to be more compact
while addressing both broken and wrong web links.

Removed any direct reference to drugs in an effort to
avoid problems from those who are humor impaired,
as well as "bots" to might flag the site as connected to drugs.

Moved the reference to the tool used by Cory to find
broken links to the thanks page.

thanks-for-help.md

@@ -4399,6 +4399,16 @@ typo/consistency fixes, improving **ALL _Makefiles_** and writing
 for your extensive efforts in helping improve the IOCCC presentation of past
 IOCCC winners and fixing almost all past entries for modern systems!
 
+Cody Boone Ferguson also used one of his own tools to detect many
+dead links.  While the tool was not perfect it went a long way
+to uncover a good number of bad, broken or otherwise invalid links.
+It was a very laborious task to copy and paste problematic links
+into the Internet Wayback Machine in an effort to try and find
+otherwise lost content.  A good number of links that now refer to
+something in the [Internet Wayback Machine](https://web.archive.org)
+archive replaced bad, broken, or otherwise invalid links thanks to
+Cody's efforts!
+
 
 ### <a name="yusuke"></a>Yusuke