Add support for MySQL notifications (fixes #3818) (#3907)

As a new configuration parameter is added, configuration version is
bumped up from 14 to 15.

The MySQL target's behaviour is identical to the PostgreSQL: rows are
deleted from the MySQL table on delete-object events, and are
created/updated on create/over-write events.

vendor/github.com/go-sql-driver/mysql/result.go

@@ -0,0 +1,22 @@
+// Go MySQL Driver - A MySQL-Driver for Go's database/sql package
+//
+// Copyright 2012 The Go-MySQL-Driver Authors. All rights reserved.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package mysql
+
+type mysqlResult struct {
+	affectedRows int64
+	insertId     int64
+}
+
+func (res *mysqlResult) LastInsertId() (int64, error) {
+	return res.insertId, nil
+}
+
+func (res *mysqlResult) RowsAffected() (int64, error) {
+	return res.affectedRows, nil
+}