set size from varchar(10) to varchar(12)

see http://www.adif.org/304/ADIF_304.htm#Mode_Enumeration and https://github.com/magicbug/Cloudlog/issues/359

application/migrations/034_col_mode_tooshort

@@ -0,0 +1,19 @@
+<?php
+defined('BASEPATH') OR exit('No direct script access allowed');
+class Migration_col_mode_tooshort extends CI_Migration {
+        public function up()
+        {
+                $fields = array(
+                        'COL_EMAIL' => array(
+                                'name' => 'COL_MODE',
+                                'type' => 'VARCHAR',
+                                'constraint' => '12',
+                        )
+                );
+                $this->dbforge->modify_column($this->config->item('table_name'), $fields);
+        }
+        public function down()
+        {
+                echo "Not possible, sorry.";
+        }
+}