Optional float-to-decimal handling & auth plugin handshake fix

New features:

  * LOAD LOCAL support
  * Allow usage of the socket backend for gen_tcp/inet
    (experimental feature in OTP/23)

Important fixes:
  * Ping response handling fixed
  * server_name_indication defaults to host option

Other:
  * Augmented and improved typing

New features:

  * Authentication method 'cached_sha2_password'
  * Reset connection command
  * Asynchronous and lazy connect modes
  * Normal exit (no error) if the server disconnects
  * Slow query logging

Important fixes:

  * Deadlock handling fixed for MySQL 5.7 

Other:

  * Travis CI tests using multiple MySQL and MariaDB versions

Various fixes

Stability and error handling fixes and some new features, e.g.

the possibility to change user and a synchronous stop function.

Main new feature: Monitor caller during transaction

OTP 21.1 compatibility

Rewrite add_packet_headers and update version

Update .app.src file and README for version 1.3.1

add erlang 20 for test