Fix [#17] Mailing job ID can not be retrieved for hook_civicrm_tokenValues() implementations.

[jensschuppe]

No description provided.

[civicrm-builder]

Can one of the admins verify this patch?

[seamuslee001]

Jenkins ok to test

[totten]

Thank you, @jensschuppe.

In reviewing this, I found that there was also a patch in civicrm/civicrm-core#12026 which was merged into civicrm-core v5.6. It addresses the same problem (i.e. mis-match in the name of the fields passed-around), but it goes the opposite way (e.g. standardizing on mailingJobId instead of mailingJob).

Overall, I think it's slightly more maintainable to pass the MailingJob ID instead of the MailingJob DAO. (There's more implicit-coupling when someone uses the DAO.) Regardless, this technique still seems useful for compatibility with <=5.5. So I merged manually and included a revision a901e6a to use it as a short-term fix.