Format fix 1980s and 1990s README.md files

I also updated the todo.md file as I left some things out that have to
be done. I only explicitly named one thing but when I go over them as a
final pass I will address the things in question (some will require
discussion).

1993/README.md

@@ -1,17 +1,17 @@
-1993 marked the "The Tenth International Obfuscated C Code Contest"
+# 1993 marked the "The Tenth International Obfuscated C Code Contest"
 
-
-Look at the README.md file for the given winner for information
-on how to compile the winner and how to run the winning program.
+Look at the README.md file for the given winning entry for information
+on how to compile it and how to run the winning program.
 Look at the winning source and try to figure how it does what it does!
 You may then wish to look at the Author's remarks for even more details.
 
-Use make to compile entries.  It is possible that on BSD or non-unix
-systems the makefile needs to be changed.  See the Makefile for details.
+Use `make` to compile entries.  It is possible that on BSD or non-Unix
+systems the Makefile needs to be changed.  See the Makefiles and/or README.md
+files for details.
 
-Read over the makefile for compile/build issues.  Your system may
-require certain changes (add or remove a library, add or remove a
-#define).
+Read over the Makefile and/or README.md files for compile/build issues.  Your
+system may require certain changes (add or remove a library, add or remove a
+`#define` i.e. the `-D` flag).
 
 Name and address information are separated from the actual program
 prior to judging.  This eliminates any chance that we would bias our
@@ -22,13 +22,13 @@ classic K&R C was allowed so long as ANSI C compilers could still
 compile the entry.  If you do not have an ANSI C compiler, you may
 not be able to compile the winners, sorry!
 
-A few notes regarding future contests:
+## A few notes regarding future contests:
 
 Be sure to wait until the 1994 rules are posted before submitting entries.
 Rules differ from year to year, sometimes in significant ways.
 
 In 1994, we will retract the guideline that discouraged the use of C
-constructs such as 3["curds"].  At one time, certain ANSI compilers did
+constructs such as `3["curds"]`.  At one time, certain ANSI compilers did
 not consider such expressions to be valid ANSI C.  Alert readers noted
 that the current ANSI standard considered them to be valid.  We were
 unable to find an ANSI C compiler that flagged such expressions as
@@ -38,8 +38,10 @@ Please send us comments and suggestions what we have expressed above.
 Also include anything else that you would like to see in future contests.
 Send such email to:
 
-	...!{sun,pacbell,uunet,pyramid}!hoptoad!judges
-	judges@toad.com
+```
+...!{sun,pacbell,uunet,pyramid}!hoptoad!judges
+judges@toad.com
+```
 
 If you use, distribute or publish these entries in some way, please drop
 us a line.  We enjoy seeing who, where and how the contest is used.
@@ -47,7 +49,7 @@ us a line.  We enjoy seeing who, where and how the contest is used.
 If you have problems with any of the entries, AND YOU HAVE A FIX, please
 email the fix (patch file or the entire changed file) to the above address.
 
-Credits:
+### Credits:
 
 We would like to thank Barbara Frezza for her role as official chef
 of the contest.  Landon Noll and Larry Bassel appreciated the opportunity