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]
Update docs, change_table does not use TableDefinition.

[ci skip]

Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
Freeze columns only once per Result

Conflicts:
	activerecord/lib/active_record/result.rb
remove unused path_without_format variable

Was forgotten in a72dab0.
Fix typo on CHANGELOG.md
Merge pull request #9528 from korny/patch-1

Fix unused variable warning in mapper.rb
Merge pull request #9531 from erik-escobedo/patch-1

Fix typo on ActionPack's ChangeLog
Backport fixes about #7774 to 3-2-stable

Fix ActionDispatch::Request#formats when HTTP_ACCEPT header is an empty
string.
Merge pull request #9543 from maximerety/backport_fix_7774

Backported #7774 to 3-2-stable