Fix auto_link() for the Nth time

 - anchor() is for local links and breaks ones that don't have a protocol prefix
 - Allow :// links (no actual protocol specified)
 - Further simplified the URL regular expression
Upload library, clean_file_name function: Fix xss bug.

For example: If you clear this string "%%3f3f" according to the $bad array will fail. The result will be "%3f"
Because str_replace() replaces left to right.

Signed-off-by: xeptor <servetozkan@live.com>
Remove str_replace in return
Merge pull request #2201 from xeptor/develop

Upload library, clean_file_name function: Fix xss bug.
Libraries' filenames must be named in a ucfirst-like manner
Merge branch 'develop' of github.com:EllisLab/CodeIgniter into develop
Update unit tests with the ucfirst-library-filename requirement
Fix issue #2179
Some micro-optimization to the Driver library loader
Fix issue #2202 and alter Loader Class docs
Adjustments in routing documentation

* fixed syntax error for "note" banner
* more useful example, in previous one there was no need for strtolower, nor for a callback
Merge pull request #2203 from vlakoff/develop

Adjustments in routing documentation
Fix list_fields seek bug

On the first list_fields call, the field pointer is moved to the end
of the list of fields. This change ensures that the pointer is
positioned at the start of the field list before grabbing the names.

Signed-off-by: Chris Buckley <chris@cmbuckley.co.uk>
Merge pull request #2204 from starsquare/develop

Fix list_fields seek bug
Replace is_file() with the faster file_exists()
(where it makes sense)

Also:
 - Implemented caching of configuration arrays for smileys, foreign characters and doctypes.
 - Implemented cascading-style loading of configuration files (except for library configs, DB and constants.php).
Merge branch 'develop' of github.com:EllisLab/CodeIgniter into develop
[ci skip] Add some changelog entries
Replace CI_Upload::clean_file_name() usage with CI_Security::sanitize_filename()

Also applied @xeptor's fix (a big thanks) to the sanitize_filename() method and added a changelog entry for it - fixes issue #73.
fixed #2207 user guide error

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Merge pull request #2208 from appleboy/userguide

fixed #2207 user guide error