Two-phase commit for 8.1

Hi,

Now that we got 8.0 out of the door, I'm submitting my two-phase commit patch 
again for discussion.

http://www.hut.fi/~hlinnaka/pgsql/

Do we want it in 8.1, if we want a short development cycle? It needs a new 
pg_twophase subdirectory, and it introduces a new system view, so I guess it 
requires an initdb (or pg_upgrade).

Any comments on the implementation or the new commands?

I would appreciate help testing the JDBC driver with an application server that 
does XA recovery properly.

- Heikki