[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to do the same thing, but became outdated.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/libraries/Email.php b/system/libraries/Email.php
index c042aaa..f8a89c3 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -421,7 +421,7 @@
 		$this->_safe_mode = ( ! is_php('5.4') && ini_get('safe_mode'));
 		$this->charset = strtoupper($this->charset);
 
-		log_message('debug', 'Email Class Initialized');
+		log_message('info', 'Email Class Initialized');
 	}
 
 	// --------------------------------------------------------------------