Log Message:
Changes 2.18.0:
* Fix memory leak when binding arrays
* Fix memory leak with ParamValues
* New cancel() method per DBI spec
* Fix memory leak in handle_old_async (missing PQclear)
* Fix memory leak in pg_db_cancel (missing PQclear)
* Mark pg_getcopydata strings as UTF8 as needed
* Function dequote_bytea returning void should not try to return something
* Fix the number of tests to skip in t/01connect.t when the $DBI_DSN
  environment variable lacks a database specification
* Fix algorithm for skipping tests in t/06bytea.t when running on a version
  of PostgreSQL lower than 9.0
* Small tweaks to get tests working when compiled against Postgres 7.4
* Fix failing test when run as non-superuser