Update the section identifier for MySQL unicode

The documentation has the correct link for the MySQL manual, but the section is 10.1.3.2 instead of the 9.1.3.2.  I'm updating this here, we should consider backporting it to the documentation for version currently supported.

http://dev.mysql.com/doc/refman/5.1/en/charset-database.html

![image](https://cloud.githubusercontent.com/assets/563721/2755176/267d2ba0-c964-11e3-8766-479d6823b966.png)