Fix typos, formatting and thank yous (add links)

In some files changed the formatting was fixed to be a proper markdown
file.

There were some typos including that some README.md files that linked to
/winners.html#Cody_Boone_Ferguson actually linked to the non-existent
file /years which obviously would not work.

I also added links to the rest of the places I have fixed entries (but
see below) and I did the same for Yusuke Endoh's fixes.

As well apparently one entry I thought he fixed to compile under modern
systems does not seem to so that entry will have to be revisited another
time. That entry was 1993/jonth.

Those are the main changes here if not all of them.

1990/theorem/README.md

@@ -11,10 +11,12 @@
 
         make all
 
-NOTE: thanks to Yusuke Endoh for the pointing out that `atof()` nowadays needs
-`#include <stdlib.h>` in order to get this to work. Thanks also to Cody Boone
-Ferguson for fixing some segfaults under modern (and in some cases earlier)
-systems with this entry.
+[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed some segfaults
+under modern (and in some cases earier) systems with this entry. Thank you Cody!
+
+[Yusuke Endoh](/winners.html#Yusuke_Endoh) pointed out that `atof` nowadays
+needs `#include <stdlib.h>` which was used in order to get this to work
+initially. Thank you Yusuke!
 
 
 ## To run: