Enforce i18n version >= v0.6.4

v0.6.2 and v0.6.3 both have issues with Ruby 1.8.7, see
https://github.com/svenfuchs/i18n/issues/192 for more info.
Backported #6755 to 3-2-stable. Don't read csv file during executing db:fixtures:load.
Merge pull request #9485 from authorNari/backport-6755-to-3-2-stable

Backported #6755 to 3-2-stable. Don't read csv file during executing db:fixtures:load.

CSV fixtures have already been removed some time ago in 1716da07204193c8acf967e2d75a53a82e4c7c28, but the task was still loading them, even though later it tried to find the related yaml file.
Improve AR changelog [ci skip]