add support of mysqlnd driver (alternative to libmysqlclient)

[remicollet]

Mostly a proof of concept (tests needed)

[patrickallaert]

I am very much in favor of supporting mysqlnd! I also think it should be the default as of APM 2.2 (new version), what is your opinion on that?

However, I think this should not be implemented as another driver, but rather defining macros that would abstract the mysql or mysqlnd API that would be used under the hood.

That way, it also prevents having both drivers at the same time, which is something I would prefer not to support.

Opinions?

[patrickallaert]

By supporting mysqlnd using macros around mysql API, this would dramatically reduce the number of lines of duplicated code.

[remicollet]

I am very much in favor of supporting mysqlnd! I also think it should be the default as of APM 2.2 (new version), what is your opinion on that?

+1 (having dependency on libmysqlclient is not friendly, especially when PHP don't have it anymore)

That way, it also prevents having both drivers at the same time, which is something I would prefer not to support.

This is already not alllowed (if ... elseif ...)

By supporting mysqlnd using macros around mysql API, this would dramatically reduce the number of lines of duplicated code.

This was only a prrof of concept ;) btw this is about lot of conditional vs duplicated code.

I will try to see if a can update this PR (time...)