New Toolbar: Stop instead of pause for streams

[Nikolaj Hald Nielsen]

>> something that also came up on FOSDEM and also just this
>> moment on IRC:
>> Pause doesn't make sense for streams, there only a stop
>> action exists. So my suggestions: replace the pause- with
>> a stop-button for streams in the new toolbar.
>>
>> This should fix that issue.
>
> Good idea, but we should special-case Last.fm streams, because you can
> actually pause them.

Not just last.fm streams. Many streams will likely become pausable and
seekable with an improved phonon backend I think. Ideally Phonon
should know what is possible for a given stream. All the Magnatune
streams are seakable for instance, and Ampache ones should be as well.

- Nikolaj