DROP NODE will now pass all nodes being dropped to the stored functions and event

This allows slony to detect if a provider that is being dropped
only provides the subscription to some other node that is also
being dropped.

Also update the unit tests to reflect the new method
of FAILOVER involving provider-only nodes

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=slony1-engine.git;a=commitdiff;h=41f71949573f4d84903059afbd25aeb7238271ad

Modified Files
--------------
clustertest/disorder/tests/Failover.js       |    2 +-
clustertest/disorder/tests/SiteFailover.js   |    4 +-
clustertest/disorder/tests/disorder_tests.js |    8 ++-
src/backend/slony1_funcs.sql                 |   89 +++++++++++++++-----------
src/slon/remote_worker.c                     |   61 ++++++++++--------
src/slonik/slonik.c                          |   47 ++++++++------
6 files changed, 121 insertions(+), 90 deletions(-)