utilize static function variables in Common::log_message() to "cache" log threshold and Log library instance to reduce function calls
diff --git a/system/core/Common.php b/system/core/Common.php
index a4b4f2b..d494caf 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -413,14 +413,23 @@
 	 */
 	function log_message($level = 'error', $message, $php_error = FALSE)
 	{
-		static $_log;
+		static $_log, $_log_threshold;
+		
+		if ($_log_threshold === NULL)
+		{
+			$_log_threshold = config_item('log_threshold');
+		}
 
-		if (config_item('log_threshold') === 0)
+		if ($_log_threshold === 0)
 		{
 			return;
 		}
 
-		$_log =& load_class('Log', 'core');
+		if ($_log === NULL)
+		{
+			$_log =& load_class('Log', 'core');
+		}
+		
 		$_log->write_log($level, $message, $php_error);
 	}
 }