Don't use globals

- Use load_class() to get objects during bootstrap process.
- Change load_class() to accept a class constructor parameter
  instead of previously unused class name prefix.
- Change CI_Router::__construct() to accept  as a parameter.
diff --git a/tests/mocks/core/common.php b/tests/mocks/core/common.php
index 9eb6b09..5c32ca5 100644
--- a/tests/mocks/core/common.php
+++ b/tests/mocks/core/common.php
@@ -65,6 +65,7 @@
 
 // --------------------------------------------------------------------
 
+/*
 if ( ! function_exists('load_class'))
 {
 	function load_class($class, $directory = 'libraries', $prefix = 'CI_')
@@ -86,6 +87,7 @@
 		return $obj;
 	}
 }
+*/
 
 // Clean up error messages
 // --------------------------------------------------------------------