pgsql: Properly document semphore requirements by accounting for worker

Properly document semphore requirements by accounting for worker
processes.

Backpatch to 9.1 and 9.0.

Submitted by Anton Yuzhaninov, confirmed by Robert Haas

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/38052a9dbc90305b8f1fa5b87cbd7099778e66ab

Modified Files
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doc/src/sgml/runtime.sgml | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)