Bump MCS API version

[Benedikt Meurer]

Olivier Fourdan wrote:
>>>>>I think we should bump the MCS API version, so old plugins aren't loaded
>>>>>anymore (i.e. the taskbar plugin, the iconbox plugin, and the temporary
>>>>>shortcuts plugin, which even causes trouble when loaded together with
>>>>>the current keyboard plugin). This will however require SVN users to
>>>>>rebuild all MCS plugins.
>>>>>
>>>>>Opinions?
>>>
>>>I'd say go for it, assuming we aren't removing/merging any other plugins
>>>before 4.4.
> 
> Yeap, I second that. It's a good idea.

Done.

> Cheers,
> Olivier.

Benedikt