All class names have been adjusted to use a phpbb_request prefix,
allowing them to be autoloaded.
Also introduces some improvements to autoloading in general.
PHPBB3-9716
The well known request_var function is now a wrapper that calls a method
on a phpbb_request object. The class provides additional functionality.
It can replace all super globals with special objects that throw errors
when being accessed. They still allow isset operations to keep backward
compatibility with isset($_POST['var']) checks. The phpbb_request class
implements the phpbb_request_interface which is available for easy mocking
of input in tests.
PHPBB3-9716
