http://en.wikipedia.org/wiki/Year_2038_problem

formatting date and time values for years >=2038 or <=1901 is now possible also with intl extension is
installed. 32bit systems will fall back to the PHP implementation because intl uses a 32bit UNIX timestamp internally.
On a 64bit system the intl formatter is used in all cases if installed.

fixes #5577

[skip ci] Fix Arabic File Type Validation Message

Added content to give a clear example to those that don't intuitively know how to set the template property using array notation.

close #6811

[skip ci] Update intro-upgrade-from-v1.md

fixes #6748

[skip ci] Fix typo in spanish translation

- ensure HTML version is acutally HTML formatted
- added valid text version

fixes #6814
original issue #6748

docs/guide/tutorial-performance-tuning.md better wordings[ci skip]

docs/guide-ja/tutorial-performance-tuning.md - added [ci skip]

* 'master' of github.com:yiisoft/yii2:
  Update test-fixtures.md
  docs/guide-ja/tutorial-mailing.md - added [ci skip]
  docs/guide/tutorial-mailing.md - corrections [ci skip]
  docs/guide/tutorial-i18n.md revised [ci skip]
  Fixed typo
  docs/guide-ja updated [ci skip]
  docs/guide-ja/tutorial-i18n.md - completed [ci skip]
  docs/guide-ja/tutorial-i18n.md - WIP
  docs/guide-ja/tutorial-i18n.md - WIP [ci skip]
  docs/guide-ja/tutorial-i18n.md - WIP [ci skip]
  Update start-hello.md
  yii\db\ActiveQuery phpDoc fix

docs/guide-ja/tutorial-mailing.md - added [ci skip]

docs/guide/tutorial-mailing.md - corrections [ci skip]

this is needed to ensure search works immediately after the insert.

docs/guide/tutorial-i18n.md revised [ci skip]

Update start-hello.md

Docs guide ja tutorial i18n [ci skip]

fix typo

yii\db\ActiveQuery phpDoc fix 2