bug 296 - part 1 FAILOVER fixes

This change allows a non-origin node to be specified on the FAILOVER command
so that subscriptions for these nodes are not redirected to the backup node.

An array of all the failed nodes (in addition to the one being failed over at this
stage of the process) is now passed to many of the failover stored functions

This commit also adds the SiteFailover unit test that tests multiple nodes in a site
failing over when the cluster does not have a complete path network

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=slony1-engine.git;a=commitdiff;h=50dcdb884c5ba7cae99a20468324809091c97394

Modified Files
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clustertest/disorder/tests/SiteFailover.js |  198 ++++++++++++++++++++++++++++
src/backend/slony1_funcs.sql               |   46 ++++---
src/slon/remote_worker.c                   |    6 +-
src/slonik/slonik.c                        |  115 +++++++++++++---
4 files changed, 331 insertions(+), 34 deletions(-)