Viddler oembed has new endpoint, old one strips maxwidth

[Otto42]

Viddler changed their oembed endpoint:

​http://developers.viddler.com/documentation/oembed/

Now it's "​http://www.viddler.com/oembed/" instead of "​http://lab.viddler.com/services/oembed/".

They have the old endpoint redirecting, but unfortunately, the redirection strips off the maxwidth (and possibly other) parameters, which can result in incorrectly sized videos when using oembed with Viddler.

Example:
​http://lab.viddler.com/services/oembed/?url=http://www.viddler.com/v/bdce8c7&format=json&maxwidth=250

Redirects to:
​http://www.viddler.com/oembed/?url=http://www.viddler.com/v/bdce8c7&format=json

We should change the endpoint in class-oembed.php to the new one. If the new endpoint is used directly, with no redirect, then it does correctly handle the maxwidth parameter.

[garhdez]

Changed endpoint for Viddler oEmbed service

[garhdez]

Just changed the endpoint for the Viddler oEmbed API.

[wonderboymusic]

In 28556:

Viddler has had a new oEmbed endpoint for at least 10 months. Let us update to it.

Props garhdez.
Fixes #24296.