Binlog compress

[fulldb]

A Pull Request should be associated with an Issue.

We wish to have discussions in Issues. A single issue may be targeted by multiple PRs.
If you're offering a new feature or fixing anything, we'd like to know beforehand in Issues,
and potentially we'll be able to point development in a particular direction.

Related issue: #884

Further notes in https://github.com/github/gh-ost/blob/master/.github/CONTRIBUTING.md
Thank you! We are open to PRs, but please understand if for technical reasons we are unable to accept each and any PR

Description

This PR [briefly explain what it does]

In case this PR introduced Go code changes:

• contributed code is using same conventions as original code
• script/cibuild returns with no formatting errors, build errors or unit test errors.

[fulldb]

Related issue:
#884

support enabled this parameter binlog_transaction_compression
support binlog_transaction_compression =on

[timvaillancourt]

@fulldb thanks for this great contribution! Is it possible to add a unit test that confirms this behaviour?

Preferably this would validate a compressed row event ends up as an event we expect