The label/title of the program that is shown in the taskbar plugin is not
shortened. If the label/title is longer than the width of the button, the
label/title is drawn over the next button in the taskbar.

Reproducible: Always
Steps to Reproduce:
1. Taskbar settings: expand to fill screen, show label
2. Open a program with a long title, e.g. sylpheed.
3. Show the taskbar plugin. The title is not cut to the button width.



Expected Results:  
The label/title shown in the taskbar plugin should be limited to the width of
the button otherwise all buttons are more or less unreadable.