PPPEXT chair change

I'd like to announce that Karl Fox has asked to step down as chair of
pppext and that James Carlson has agreed to take over as new
chair. I'd like to thank Karl for the many _years_ of service he's put
into this WG and to the PPP effort in general. I'd also like to
welcome James, hardly a newcomer to this WG!

One of the things that we'll need to do relatively quickly is to have a
look at the WG charter & milestones and have a discussion about what
this WG can and should be doing.

Thomas