[ci skip] DocBlocks for DB drivers' utility classes

Partially fixes issue #1295.
diff --git a/system/database/drivers/oci8/oci8_utility.php b/system/database/drivers/oci8/oci8_utility.php
index 0c6cfc6..e5aae81 100644
--- a/system/database/drivers/oci8/oci8_utility.php
+++ b/system/database/drivers/oci8/oci8_utility.php
@@ -35,12 +35,17 @@
  */
 class CI_DB_oci8_utility extends CI_DB_utility {
 
+	/**
+	 * List databases statement
+	 *
+	 * @var	string
+	 */
 	protected $_list_databases	= 'SELECT username FROM dba_users'; // Schemas are actual usernames
 
 	/**
-	 * Oracle Export
+	 * Export
 	 *
-	 * @param	array	Preferences
+	 * @param	array	$params	Preferences
 	 * @return	mixed
 	 */
 	protected function _backup($params = array())