* Second batch of leechx implementation.

* Fully disentangled leech.php and leechx.php code, dropped dirlist.php.
* Use special `keep slashes´ double encoding for rewritable EZ-Leech URLs.
* Removing the filename part from a EZ-Leech URL now retrieves a non-recursive plain HTML directory listing.
* Adapted Apache rewrite rules to accommodate new EZ-Leech URL schemes.