Added support for PostgreSQL 9.2

PostgreSQL 9.2 changed removed the `current_query` column from `pg_stat_activity` and replaced it with two new columns: `query` which shows the current or last query, and `status` which shows whether it's active or idle. I've added a new separate `check_postgresql_92.py` script to handle the difference in fields. The script takes exactly the same arguments and outputs exactly the same results, so if someone upgrades to a newer version of postgres they only need to change script names.