vacuumlo: Use a cursor to limit client-side memory usage.
vacuumlo: Use a cursor to limit client-side memory usage.

This prevents the client from gobbling up too much memory when the
number of large objects to be removed is very large.

Andrew Dunstan, reviewed by Josh Kupershmidt

Postgres-XL/Postgres-XL,techdragon/Postgres-XL,greenplum-db/gpdb,greenplum-db/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,ovr/postgres-xl,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,jmcatamney/gpdb,adam8157/gpdb,oberstet/postgres-xl,pavanvd/postgres-xl,xinzweb/gpdb,xinzweb/gpdb,adam8157/gpdb,yazun/postgres-xl,Postgres-XL/Postgres-XL,jmcatamney/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,pavanvd/postgres-xl,yazun/postgres-xl,lisakowen/gpdb,ashwinstar/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,pavanvd/postgres-xl,zeroae/postgres-xl,lisakowen/gpdb,xinzweb/gpdb,zeroae/postgres-xl,techdragon/Postgres-XL,50wu/gpdb,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,ashwinstar/gpdb,adam8157/gpdb,xinzweb/gpdb,ovr/postgres-xl,50wu/gpdb,ovr/postgres-xl,oberstet/postgres-xl,lisakowen/gpdb,pavanvd/postgres-xl,zeroae/postgres-xl,ashwinstar/gpdb,ashwinstar/gpdb,lisakowen/gpdb,yazun/postgres-xl,adam8157/gpdb,50wu/gpdb,techdragon/Postgres-XL,Postgres-XL/Postgres-XL,ashwinstar/gpdb,ovr/postgres-xl,ashwinstar/gpdb,50wu/gpdb,xinzweb/gpdb,50wu/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,techdragon/Postgres-XL,yazun/postgres-xl,Postgres-XL/Postgres-XL,ovr/postgres-xl,jmcatamney/gpdb,ashwinstar/gpdb,50wu/gpdb,lisakowen/gpdb,zeroae/postgres-xl,Postgres-XL/Postgres-XL,greenplum-db/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,oberstet/postgres-xl,yazun/postgres-xl,jmcatamney/gpdb,oberstet/postgres-xl