Fix visibiliy of option_allow_private_messages in admin page

Keep ‘qa-top-users-item’ class, use wrapper class for each page type.

Fix unencoded URLs not being detected when closing questions

Do not log security form violations unless in debug mode

Fix a_unselect not being called when hiding selected answer

Fixes #443.
Extract output buffering to function.
Use regular buffering if gzip option not set.
Use buffering in AJAX requests, to avoid “headers already sent” warning
in some situations.

Fix session_start after output started

Fixes #439

Let user input a confirmation code manually

Include confirmation code in confirmation email

No longer supporting PHP 5.1.
Fixes #394

Fixes #472

Fixes #425