At the moment, a bundle can be configured in PHP, YAML and XML.
Here, I'm talking only about the bundle configuration. Not about routing
or services. It means I only refer to the app/config/config.xml file.

So basically, I'm talking about this configuration.

I made a quick poll around me (SensioLabs) and nobody have ever seen a
configuration in XML. Some were not even aware that was possible.

Therefore I would like to deprecate and remove the support of XML for the
bundle configuration (only).

YAML is de-facto the standard for it. And the PHP way is mandatory to tweak the
container in a bundle extension, or a compile pass.

What do you think?