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/system/core/URI.php b/system/core/URI.php
index 3b7718f..309c776 100644
--- a/system/core/URI.php
+++ b/system/core/URI.php
@@ -102,23 +102,21 @@
 				return;
 			}
 
-			// Let's try the REQUEST_URI first, this will work in most situations
+			// Is there a PATH_INFO variable? This should be the easiest solution.
+			if (isset($_SERVER['PATH_INFO']))
+			{
+				$this->_set_uri_string($_SERVER['PATH_INFO']);
+				return;
+			}
+
+			// Let's try REQUEST_URI then, this will work in most situations
 			if (($uri = $this->_parse_request_uri()) !== '')
 			{
 				$this->_set_uri_string($uri);
 				return;
 			}
 
-			// Is there a PATH_INFO variable?
-			// Note: some servers seem to have trouble with getenv() so we'll test it two ways
-			$uri = isset($_SERVER['PATH_INFO']) ? $_SERVER['PATH_INFO'] : @getenv('PATH_INFO');
-			if (trim($uri, '/') !== '' && $uri !== '/'.SELF)
-			{
-				$this->_set_uri_string($uri);
-				return;
-			}
-
-			// No PATH_INFO?... What about QUERY_STRING?
+			// No REQUEST_URI either?... What about QUERY_STRING?
 			if (($uri = $this->_parse_query_string()) !== '')
 			{
 				$this->_set_uri_string($uri);