Fixes compilation failure with pre-5.7 C API

[dbadapt]

When compiling against a MySQL C API prior to 5.7, the compilation
fails due to the reference to MYSQL_TYPE_JSON.

This patch will conditionally compile support for MYSQL_TYPE_JSON
only if it is supported in the underlying C API.

Resolves: Bug #80539

[mysql-oca-bot]

Hi, thank you for submitting this pull request. In order to consider your code we need you to sign the Oracle Contribution Agreement (OCA). Please review the details and follow the instructions at http://www.oracle.com/technetwork/community/oca-486395.html
Please make sure to include your MySQL bug system user (email) in the returned form.
Thanks

[dbadapt]

I think this should be covered under the blanket Percona LLC OCA, I will verify on Monday.

[mysql-admin]

Hi David,
You are covered by the Percona OCA but you are not registered in bugs.mysql.com. Please register at https://dev.mysql.com/auth/register/ with the email included in the OCA so this contribution can be processed.

Thanks
==Omer

[dbadapt]

Omer, I logged into my Oracle account and visited the link. It redirected me to http://dev.mysql.com/ did this do the trick or do I need to create a new account?

[mysql-oca-bot]

Hi, thank you for your contribution. Please confirm this code is submitted under the terms of the OCA (Oracle's Contribution Agreement) you have previously signed by cutting and pasting the following text as a comment:
"I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it."
Thanks

[mysql-admin]

Hi David,
Yes now you are 'linked' to the Perocna OCA. Now just confirm the above is submitted under its terms and we are set

Thanks
==Omer

[dbadapt]

"I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it."

[mysql-oca-bot]

Hi, thank you for your contribution. Your code has been assigned to an internal queue. Please follow
bug http://bugs.mysql.com/bug.php?id=80751 for updates.
Thanks