Fix small query-lifespan memory leak introduced by 8.4 change in index AM API for bitmap index scans.  Per report and test case from Kevin Grittner.
Fix small query-lifespan memory leak introduced by 8.4 change in index AM API
for bitmap index scans.  Per report and test case from Kevin Grittner.

greenplum-db/gpdb,lisakowen/gpdb,edespino/gpdb,xinzweb/gpdb,yuanzhao/gpdb,50wu/gpdb,techdragon/Postgres-XL,Chibin/gpdb,jmcatamney/gpdb,kmjungersen/PostgresXL,kmjungersen/PostgresXL,arcivanov/postgres-xl,yuanzhao/gpdb,postmind-net/postgres-xl,yazun/postgres-xl,jmcatamney/gpdb,kmjungersen/PostgresXL,greenplum-db/gpdb,50wu/gpdb,ovr/postgres-xl,Chibin/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,Postgres-XL/Postgres-XL,yuanzhao/gpdb,zeroae/postgres-xl,xinzweb/gpdb,greenplum-db/gpdb,edespino/gpdb,oberstet/postgres-xl,50wu/gpdb,xinzweb/gpdb,pavanvd/postgres-xl,yuanzhao/gpdb,arcivanov/postgres-xl,greenplum-db/gpdb,ashwinstar/gpdb,Chibin/gpdb,oberstet/postgres-xl,tpostgres-projects/tPostgres,pavanvd/postgres-xl,jmcatamney/gpdb,xinzweb/gpdb,kmjungersen/PostgresXL,Chibin/gpdb,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,jmcatamney/gpdb,50wu/gpdb,Chibin/gpdb,ashwinstar/gpdb,tpostgres-projects/tPostgres,Chibin/gpdb,edespino/gpdb,edespino/gpdb,jmcatamney/gpdb,yazun/postgres-xl,techdragon/Postgres-XL,snaga/postgres-xl,arcivanov/postgres-xl,lisakowen/gpdb,ashwinstar/gpdb,yazun/postgres-xl,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,ashwinstar/gpdb,snaga/postgres-xl,postmind-net/postgres-xl,tpostgres-projects/tPostgres,lisakowen/gpdb,oberstet/postgres-xl,adam8157/gpdb,tpostgres-projects/tPostgres,greenplum-db/gpdb,techdragon/Postgres-XL,yazun/postgres-xl,50wu/gpdb,Chibin/gpdb,ovr/postgres-xl,edespino/gpdb,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,Postgres-XL/Postgres-XL,zeroae/postgres-xl,edespino/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,snaga/postgres-xl,50wu/gpdb,yuanzhao/gpdb,pavanvd/postgres-xl,techdragon/Postgres-XL,Chibin/gpdb,kmjungersen/PostgresXL,oberstet/postgres-xl,Postgres-XL/Postgres-XL,lisakowen/gpdb,edespino/gpdb,zeroae/postgres-xl,arcivanov/postgres-xl,edespino/gpdb,xinzweb/gpdb,yuanzhao/gpdb,techdragon/Postgres-XL,50wu/gpdb,zeroae/postgres-xl,adam8157/gpdb,lisakowen/gpdb,snaga/postgres-xl,pavanvd/postgres-xl,edespino/gpdb,adam8157/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,ovr/postgres-xl,ashwinstar/gpdb,adam8157/gpdb,adam8157/gpdb,Chibin/gpdb,zeroae/postgres-xl,50wu/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,lisakowen/gpdb,xinzweb/gpdb,postmind-net/postgres-xl,arcivanov/postgres-xl,Postgres-XL/Postgres-XL,yuanzhao/gpdb,ovr/postgres-xl,greenplum-db/gpdb,postmind-net/postgres-xl,tpostgres-projects/tPostgres,snaga/postgres-xl,ovr/postgres-xl,xinzweb/gpdb,edespino/gpdb,yazun/postgres-xl,adam8157/gpdb,yuanzhao/gpdb,Chibin/gpdb,arcivanov/postgres-xl,jmcatamney/gpdb,ashwinstar/gpdb