Release v2.9.2

[![Build Status](https://travis-ci.org/doctrine/dbal.svg?branch=v2.9.2)](https://travis-ci.org/doctrine/dbal)

This release fixes regressions introduced in v2.9.1.

- Total issues resolved: **2**

**MySQL, Schema Introspection:**

 - [3410: MySqlSchemaManager::parseCreateOptions() must be of the type string, null given](https://github.com/doctrine/dbal/issues/3410) thanks to @jarnovanleeuwen and @morozov

**MySQL, Schema Comparison:**

 - [3414: Schema migration doesn't detect index length change](https://github.com/doctrine/dbal/issues/3414) thanks to @leofeyer and @morozov