pgsql: Fix upper limit of superuser_reserved_connections, add limit for

Fix upper limit of superuser_reserved_connections, add limit for wal_senders

Should be limited to the maximum number of connections excluding
autovacuum workers, not including.

Add similar check for max_wal_senders, which should never be higher than
max_connections.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/64d64a0530a57b4f949fc6d96ebc8d8318b63cdb

Modified Files
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doc/src/sgml/config.sgml            |   16 ++++++++++------
src/backend/postmaster/postmaster.c |    7 ++++++-
2 files changed, 16 insertions(+), 7 deletions(-)