Support System.Transactions about mysqlconnector

[bgrainger]

It appears that System.Transactions is coming to .NET Core dotnet/corefx#10089 so implementing this will be useful for all platforms.

[bgrainger]

MySQL XA Transactions may be a good way to implement TransactionScope.

[bgrainger]

Implemented in 0.18.0.

[sidhoda]

@bgrainger is there still the possibility this could be implemented without XA transactions, like MySql.Data? Some of the restrictions with XA make it look less attractive option, particularly if running MySQL prior to 5.7.7 and using replication: https://dev.mysql.com/doc/refman/5.7/en/xa-restrictions.html

[bgrainger]

It's possible; I've created #254 to track it. If this is affecting you, could you please add a comment there to describe the specific issues you're running into? (MySQL 5.7.9 was the first GA release, so I'm not extremely concerned about limitations/errors in 5.7.x versions prior to that.)

I'm open to receiving a PR that implements a non-XA implementation of IEnlistmentNotification in order to support TransactionScope without using XA transactions.

An alternative of course is to explicitly use BeginTransaction/Commit in client code that doesn't want distributed transactions (which is a core feature of TransactionScope and part of the point of using it in the first place).