On Postgres, get_recordset_sql loads all the results into memory
(within the Postgres library, which doesn't count towards the PHP
memory limit, but does count towards making your server run out of
memory) as soon as the query completes.
This commit changes the code to use cursors, which in Postgres
allow the results to be returned in smaller chunks (by default
100,000 rows).
PostgreSQL 9.1 allows hex formating for binary which is handled better
by pg_query_params().
Getting bytea isn't required on connection, it can be used as pg_field_type()
when binary needs to be checked.
