Handle parser errors by emitting error and closing connection

This changeset makes the parser more robust by splitting on individual package boundaries and handles parser errors by emitting error and closing connection. This should have no effect for well-behaving servers, but makes our parser more robust for misbehaving servers or servers sending invalid data (intentionally or otherwise).

Together with the analysis in ticket https://github.com/friends-of-reactphp/mysql/issues/123 and the work done in #158, you're looking at around two days of work, enjoy!

Builds on top of #158 Refs #123

friends-of-reactphp / mysql

Handle parser errors by emitting error and closing connection #159