Integrating XOAUTH plugin into upstream

[Àlex Fiestas]

Hi everybody

Now that XOAUTH is starting to be used by different providers I'm wondering if 
we could integrate the XOAUTH plugin Bill developed into upstream.

I could help in any C and testing tasks but I'm lacking autotools knowledge 
that somebody else should provide (I guess I could learn but that will take 
longer time than if somebody else does).

Is anyone else interested?

https://github.com/sweetums/SASL-OAuth

Merge the pull request to make it compile with jansson2.x

Cheers.