[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to do the same thing, but became outdated.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/Form_validation.php b/system/libraries/Form_validation.php
index f731544..7c9561c 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -146,7 +146,7 @@
 		// Automatically load the form helper
 		$this->CI->load->helper('form');
 
-		log_message('debug', 'Form Validation Class Initialized');
+		log_message('info', 'Form Validation Class Initialized');
 	}
 
 	// --------------------------------------------------------------------