Add fuzzer (#1097)

The fuzzer targets the `Open` function, which can be run locally as well as through oss-fuzz's infrastructure.

fuzz.go

@@ -0,0 +1,24 @@
+// Go MySQL Driver - A MySQL-Driver for Go's database/sql package.
+//
+// Copyright 2020 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/.
+
+// +build gofuzz
+
+package mysql
+
+import (
+	"database/sql"
+)
+
+func Fuzz(data []byte) int {
+	db, err := sql.Open("mysql", string(data))
+	if err != nil {
+		return 0
+	}
+	db.Close()
+	return 1
+}