Fixes in html files in 1986/marshall

This includes the compilers.html and index.html file.

I also threw in a slight formatting change in the thanks file.

thanks-for-help.html

@@ -5171,7 +5171,7 @@ helped improve the presentation of their fellow IOCCC entries.</p>
 Ferguson</a> who is responsible for many
 improvements and fixes, including entries that no longer worked
 and other important fixes, often <strong>EXTREMELY HARD</strong> (for certain
-definitions of ‘<em>HARD</em>’ :-) ), such as
+definitions of ‘<code>HARD</code>’ :-) ), such as
 <a href="thanks-for-help.html#1988_phillipps">1988/phillipps</a>,
 <a href="thanks-for-help.html#1992_vern">1992/vern</a>,
 <a href="thanks-for-help.html#2001_anonymous">2001/anonymous</a>,