bump license to GPL v3+

[Jan Nieuwenhuizen]

As you may be aware by now, using the GPL v2 is becoming somewhat
problematic.

In order to fix future compatibility problems, GNU packages' policy 
defiance and general confusion, we have just bumped the license to 
GPL v3+ in master.

The license bump patches are all signed-off by

    Han-Wen Nienhuys
    Jan Nieuwenhuizen
    John Mandereau
    Graham Percival
    Reinhold Kainhofer
    Joe Neeman
    Heikki Johannes Junes
    Neil Puttock
    Carl D. Sorensen
    Mats Bengtsson
    Werner Lemberg
    Patrick McCarty
    Nicolas Sceaux

If you have any questions or ideas on this, please send private mail to 
Jan & Han-Wen to prevent lengthy public discussions.

Jan and Han-Wen