Resolve _protect_identifiers()/protect_identifiers() usage issues
diff --git a/system/database/drivers/mysql/mysql_forge.php b/system/database/drivers/mysql/mysql_forge.php
index 0f251b0..a907b20 100644
--- a/system/database/drivers/mysql/mysql_forge.php
+++ b/system/database/drivers/mysql/mysql_forge.php
@@ -151,7 +151,7 @@
 
 		if (count($primary_keys) > 0)
 		{
-			$key_name = $this->db->_protect_identifiers(implode('_', $primary_keys));
+			$key_name = $this->db->protect_identifiers(implode('_', $primary_keys));
 			$sql .= ",\n\tPRIMARY KEY ".$key_name.' ('.implode(', ', $this->db->protect_identifiers($primary_keys)).')';
 		}
 
@@ -161,12 +161,12 @@
 			{
 				if (is_array($key))
 				{
-					$key_name = $this->db->_protect_identifiers(implode('_', $key));
-					$key = $this->db->_protect_identifiers($key);
+					$key_name = $this->db->protect_identifiers(implode('_', $key));
+					$key = $this->db->protect_identifiers($key);
 				}
 				else
 				{
-					$key_name = $this->db->_protect_identifiers($key);
+					$key_name = $this->db->protect_identifiers($key);
 					$key = array($key_name);
 				}