Minor tweaks to docs
Merge branch 'master' of ssh://git.postgresql.org/slony1-engine
Bug #281 - improve documentation on performance implications of PATHs

Add in material describing the effects of having fully versus less-fully connected path networks
Only include the libpq header directory OR the server header directory but not both

This addresses bug 315 where a debian install had libpq-dev 9.3 installed
and postgresql-server-dev 8.4 installed.  The libpq headers are in /usr/include/postgresql
but the server headers are in /usr/lib/postgresql/8.4/server.

configure checks were failing because we were pulling in a mixutre of headers
from both versions.  The only slony component that needs the server
headers are the backend functions and they shouldn't need to use libpq headers.

This patch sets CPPFLAGS as approriate for one or the other but not both
Note that upgrade process implies an application outage
The UPDATE FUNCTIONS upgrade from a 2.1.x (or 2.0.x) Slony to 2.2.0 does not
create the no_failed column in sl_node.
Fix for endless restart loop on FAILOVER (bug 318).

If the backup node is not the most advanced, function
failedNode() will trigger a slon restart even if it
did not make any changes to the configuration because
of a missing WHERE clause.
adding in tests for bug 318