Update COPYING file
The current license for this component is out of date. Please see xfce4-taskmanager Issue #49 for additional details & discussion.
Briefly:
Comparing the 17 years old file with the new one, we have:
- some white-space changes
- a new FSF address
- some extra commas
All references to GNU Library General Public License have been replaced with GNU Lesser General Public License
cc: @aekoroglu