[ticket/13280] Properly format the current page and add sanitizer to tests

PHPBB3-13280
[ticket/13280] Correctly format user page for build_url()

PHPBB3-13280
[ticket/13280] Add additional sanitizer for ampersands in server superglobal

PHPBB3-13280
Merge pull request #41 from marc1706/ticket/13280

Ticket/13280