[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to do the same thing, but became outdated.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/core/Lang.php b/system/core/Lang.php
index fe1dc1a..3213478 100644
--- a/system/core/Lang.php
+++ b/system/core/Lang.php
@@ -69,7 +69,7 @@
 	 */
 	public function __construct()
 	{
-		log_message('debug', 'Language Class Initialized');
+		log_message('info', 'Language Class Initialized');
 	}
 
 	// --------------------------------------------------------------------
@@ -172,7 +172,7 @@
 		$this->is_loaded[$langfile] = $idiom;
 		$this->language = array_merge($this->language, $lang);
 
-		log_message('debug', 'Language file loaded: language/'.$idiom.'/'.$langfile);
+		log_message('info', 'Language file loaded: language/'.$idiom.'/'.$langfile);
 		return TRUE;
 	}