Merge from vendor branch TNF:

Merge from vendor branch TNF:
Import PostgreSQL 9.0 monitoring modules as databases/postgresql90-monitoring

This package provides the following PostgreSQL modules:
  - auto_explain
  - pg_buffercache
  - pg_stat_statements
  - pgstattuple

The "auto_explain" module provides a means for logging execution
plans of slow statements automatically, without having to run
EXPLAIN(7) by hand. This is especially helpful for tracking down
un-optimized queries in large applications.

The "pg_buffercache" module provides a means for examining what's
happening in the shared buffer cache in real time.

The "pg_stat_statements" module provides a means for tracking
execution statistics of all SQL statements executed by a server.

The "pgstattuple" module provides various functions to obtain
tuple-level statistics.