Fix failure of executor/hashjoin.h to compile standalone.
Fix failure of executor/hashjoin.h to compile standalone.

Noted while experimenting with cpluspluscheck.

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