Fix #1540

Removed redundant assignments so that the Contact Details box in profile
gets hidden when needed.
https://github.com/mybb/mybb/issues/1540
Modify it a bit

...
Fixes #1233
Fix #1590

No "Use Default" option in ACP's language preference.
https://github.com/mybb/mybb/issues/1590
Fix #1600

Removed unnecessary `` which cause problems with pgsql.
https://github.com/mybb/mybb/issues/1600
Fixes #1606 - Email with subject bug
Fix #1617 Sanitize input from MyBB server
Fixed missing htmlspecialchars_uni for #1304.
Fixes escaping of latest news.
Fixed description and link escaping.
Fixed indentation.
Using post parser to parse/filter HTML.
Fix #1617 Sanitize input from MyBB server
Fix #1617 Sanitize input from MyBB server
Fixes #1233 For AdminCP
Using description when caching instead of content.
Changing how username is escaped to allow the use of the raw variable.
Merge pull request #1619 from euantorano/fix-1304-announcement-username

Fix 1304 announcement username
Fixing double sanitizing
Remove Useless codes.