[ticket/13192] Add method for generating valid user page links based on mod_rewrite
* marc1706/ticket/13192:
[ticket/13192] Add test for app.php in external subfolder
[ticket/13192] Use ltrim() instead of preg_replace()
[ticket/13192] Order test cases consistently
[ticket/13192] Remove app.php on mod rewrite even if app.php is outside root
[ticket/13192] Pass correct parameters and rename method to get_valid_page
[ticket/13192] Use get_valid_user_page in confirm_box() and cleanup globals
[ticket/13192] Use get_valid_user_page method in build_url function
[ticket/13192] Add method for generating valid user page links
The symfony routing component allows us to use the path "/" for routes.
Therefore, we should be able to use example.com/app.php/ for controllers.
However, this currently does not properly work. The method get_web_root_path
incorrectly returns phpbb_root_path. Therefore, paths to images or files are
broken.
PHPBB3-12004
