Minor rewording in some YYYY/README.md files

This change was already applied in the README.md files of the years <
2000, yesterday, but I got tired of doing it manually as I do each year
so I used my sgit tool (https://github.com/xexyl/sgit) like:

    sgit -e 's/\(Look at the README.md file for the given\) winner/\1 winning entry/g' -e \
    's/\(on how to compile\) the winner/\1 it/g' .

which changed the text:

    ... for the given winner

and

    on how to compile the winner

to

    ... for the winning entry

and

    ... on how to compile it

This felt useful because the winner is not the entry itself but the
author (and in some cases authors). This should be clearer now. When I
do a final pass I will check for any consistency issues in the ones
changed manually.

In this commit the year 2013/README.md was format fixed as the change
was done in this file, manually, yesterday, when I did format fixes but
which was not committed as I wanted to do it with the years 2000+.

2000/README.md

@@ -1,11 +1,10 @@
-2000 marked the "The Fifteenth International Obfuscated C Code Contest"
+# 2000 marked the "The Fifteenth International Obfuscated C Code Contest"
 
 
-Standard IOCCC stuff
---------------------
+## Standard IOCCC stuff
 
-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.