pgsql: Fix handling of pg_stat_statements.stat temporary file

Fix handling of pg_stat_statements.stat temporary file

Write the file to a temporary name and then rename() it into the
permanent name, to ensure it can't end up half-written and corrupt
in case of a crash during shutdown.

Unlink the file after it has been read so it's removed from the data
directory and not included in base backups going to replication slaves.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/785b8d6ab312e5bee0846094fe06982c1d4c07f2

Modified Files
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contrib/pg_stat_statements/pg_stat_statements.c |   22 +++++++++++++++++++---
1 files changed, 19 insertions(+), 3 deletions(-)