added ability to "extend" helpers
* modified Loader to check for prefixed helpers in application/helpers folder
* surrounded provided helper functions with if (! function_exists('foo')) conditionals so the user's helper functions take precedent.
diff --git a/system/libraries/Loader.php b/system/libraries/Loader.php
index 320a43a..a59d6e3 100644
--- a/system/libraries/Loader.php
+++ b/system/libraries/Loader.php
@@ -366,8 +366,23 @@
 			{

 				continue;

 			}

+			

+			$ext_helper = APPPATH.'helpers/'.config_item('subclass_prefix').$helper.EXT;

 

-			if (file_exists(APPPATH.'helpers/'.$helper.EXT))

+			// Is this a helper extension request?			

+			if (file_exists($ext_helper))

+			{

+				$base_helper = BASEPATH.'helpers/'.$helper.EXT;

+				

+				if ( ! file_exists($base_helper))

+				{

+					show_error('Unable to load the requested file: helpers/'.$helper.EXT);

+				}

+				

+				include_once($ext_helper);

+				include_once($base_helper);

+			}

+			elseif (file_exists(APPPATH.'helpers/'.$helper.EXT))

 			{ 

 				include_once(APPPATH.'helpers/'.$helper.EXT);

 			}