pgsql: Update "Using EXPLAIN" documentation examples using current code

Update "Using EXPLAIN" documentation examples using current code.

It seems like a good idea to update these examples since some fairly
basic planner behaviors have changed in 9.3; notably that the startup cost
for an indexscan plan node is no longer invariably estimated at 0.00.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/244c8b466a743d1ec18a7d841bf42669699b3b56

Modified Files
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doc/src/sgml/perform.sgml |  166 ++++++++++++++++++++++++---------------------
1 file changed, 89 insertions(+), 77 deletions(-)