Support Polldaddy's short URL format as a whitelisted oEmbed provider.

Props donncha.
Fixes #28283.



git-svn-id: https://develop.svn.wordpress.org/trunk@28555 602fd350-edb4-49c9-b593-d223f7449a82
Viddler has had a new oEmbed endpoint for at least 10 months. Let us update to it.

Props garhdez.
Fixes #24296.


git-svn-id: https://develop.svn.wordpress.org/trunk@28556 602fd350-edb4-49c9-b593-d223f7449a82