Changed URI auto-detection to try PATH_INFO first

(thanks to @sourcejedi, PR #1326)

Up until PHP 5.2.4 (which is our new lowest requirement),
there was a bug related to PATH_INFO which made REQUEST_URI
a more reliable choice. This is now no longer the case,
see https://bugs.php.net/bug.php?id=31892 for more details.

Also removed ORIG_PATH_INFO from the suggested alternatives
for uri_protocol in application/config/config.php as it will
not exist in most of PHP's recent versions and is pointless
when you can use PATH_INFO anyway.
diff --git a/application/config/config.php b/application/config/config.php
index 6867cee..0562953 100644
--- a/application/config/config.php
+++ b/application/config/config.php
@@ -64,10 +64,9 @@
 |
 | 'AUTO'		Default - auto detects
 | 'CLI' or 'argv'	Uses $_SERVER['argv'] (for php-cli only)
-| 'REQUEST_URI'		Uses $_SERVER['REQUEST_URI']
 | 'PATH_INFO'		Uses $_SERVER['PATH_INFO']
+| 'REQUEST_URI'		Uses $_SERVER['REQUEST_URI']
 | 'QUERY_STRING'	Uses $_SERVER['QUERY_STRING']
-| 'ORIG_PATH_INFO'	Uses $_SERVER['ORIG_PATH_INFO']
 |
 */
 $config['uri_protocol']	= 'AUTO';