systray: split xembed part into own file, prepare to receive d-bus
There is a new d-bus systray spec by KDE that is less retarded. It's used by KDE and other environments such as Ubuntu's Unity. We'll integrate code to have E17 to support this spec, then we must separate the XEmbed part into its own file to avoid confusion.
Patch by: Gustavo Sverzut Barbieri <barbieri@…>