Support MySQL 5.5

Summary:
116.utf8.sql throws this under MySQL 5.5:

Column length too big for column 'keyBody' (max = 21845); use BLOB or TEXT instead

I guess that's because MySQL 5.5 changed maximum length of UTF-8 character from 3 bytes to 4.

I've updated also 116.utf8.sql for people with new installs.

Test Plan:

upgrade_schema.php

Reviewers: epriestley

Reviewed By: epriestley

CC: aran

Differential Revision: https://secure.phabricator.com/D2117