Update user_agents.php

Added the PS Vita User Agent to the list.
Made set_error() method DRY.
Reverted indenting spaces back to tabs.

(My fault - Sorry!)
fix typos in Parser.php
Removed unused variable $name in Cache_memcached.php
Update Profiler.php to show HTTP_DNT status

show do not track header status
Optimize Change Log, add entry for 2.1.4
Upgrade notes for 2.1.4
Update Downloads page

Even though it's useless right now...
Update GitHub "tags" link to new Releases feature.
Merge branch 'refs/heads/develop' into update/changelog

Conflicts:
	user_guide_src/source/changelog.rst
	user_guide_src/source/installation/downloads.rst
	user_guide_src/source/installation/upgrade_214.rst
Merge doc changes; small related updates.
Merge pull request #2524 from cryode/update/changelog

Fix & Update Change Log; add 2.1.4 info where necessary.
[ci skip] Revert some cosmetic changes from PR #2524, for consistency
[ci skip] Adding another cyrillic character to config/foreign_chars.php (#2509)
Merge pull request #2502 from enapupe/patch-1

Update Profiler.php to show HTTP_DNT status
Add changelog entry for PR #2502
Merge pull request #2417 from thefuzzy0ne/fix/upload_dry

Fix/upload dry
Merge pull request #2411 from Dumk0/patch-1

fix typos in Parser.php
Merge pull request #2452 from thallisphp/patch-3

Removed unused variable $name in Cache_memcached.php