[ci skip] Change some log messages' level

'Class Loaded' type of messages flood log files when
log_threshold is set to 2 (debug). They're now logged
as 'info' level.

This is manually applying PR #1528, which was created
to do the same thing, but became outdated.
diff --git a/system/database/DB_utility.php b/system/database/DB_utility.php
index 963080f..4bf94d4 100644
--- a/system/database/DB_utility.php
+++ b/system/database/DB_utility.php
@@ -87,7 +87,7 @@
 	public function __construct(&$db)
 	{
 		$this->db =& $db;
-		log_message('debug', 'Database Utility Class Initialized');
+		log_message('info', 'Database Utility Class Initialized');
 	}
 
 	// --------------------------------------------------------------------