Update lang.php (FR translation's one)

autor duplicated + < and > fixes.

Translation update (fr)

Update lang.php (FR translation's one)

* contributors duplication
* adding myself to the contributors' list
* typo

Translation update (th)

The token login was introduced for the flash uploader. Since it has been
removed there is no need for this code anymore.

[WiP] Deactivate XSS-Protection during preview

Skips one (sometimes flaky) redirect

Translation update (fr)

Translation update (zh)

Translation update (de)

Translation update (de)

Translation update (pt-br)

Translation update (cs)

* Added missing 'userchangefail' in English to authad.

Fix typo in Spanish ACL help.txt

Updated a word wrongly written on spanish

Translation update (es)

Translation update (ja)

Add an in-progress class to the quicksearch form.

Translation update (ru)

Show specific error messages if user creation fails

The motivation is to work around/fix issue #1182.

Using a CSP-Header did not work.

ToDo:
- [ ] Implement a check for Chrome only.