When integrating PULL-527 (and sisters) some sections of current environment.xml file has been detected as "delete-able".
This FEEDBACK section of mysql shows one custom message about the upgrade to unicode that happened in Moodle 1.6. Right now it simply hasn't sense so:
1) In the 3 currently supported branches (19_STABLE, 20_STABLE and master), take rid of those custom FEEDBACKs within the Moodle 2.0 and Moodle 2.1 sections.
2) In the 20_STABLE and master branches, delete the 'mysql416required' string.