Support Go MySQL Stored Procedure calls

[ykcadcg]

Issue description

Tell us what should happen and what happens instead
Wanted to call my sproc in go, given error

Example code

call mysproc();

Error log

not supported```

### Configuration
*Driver version (or git SHA):*

*Go version:* run `go version` in your console
Go 1.8.1

*Server version:* E.g. MySQL 5.6, MariaDB 10.0.20
MySQL 6

*Server OS:* E.g. Debian 8.1 (Jessie), Windows 10
Windows/ Ubuntu

[pjebs]

@arnehormann With multi-read support now implemented, will calling stored procedures now work?

[arnehormann]

@pjebs honestly, I don't know. I'm a little behind right now and running low on time for open source. I hope that will change soon, but as it is now, it already frustrates me that I can't even finish #302 - which is a priority for me in the driver.
You can always just try it - the pieces should be there 😉

[andizzle]

just FYI this is working now.

[ericleb010]

Is it working? Whenever I call an otherwise-working stored procedure, no error is returned, yet the operation was not completed and a lock was left on the database (preventing me from calling this procedure manually).

[andizzle]

Is it possible that you have not set autocommit to true?

[ericleb010]

Looks like that was the case... good call.

[pjebs]

https://golang.org/pkg/database/sql/#Out