Ensure generic plan gets used for a plpgsql expression with no parameters.
Ensure generic plan gets used for a plpgsql expression with no parameters.

Now that a NULL ParamListInfo pointer causes significantly different
behavior in plancache.c, be sure to pass it that way when the expression
is known not to reference any plpgsql variables.  Saves a few setup
cycles anyway.

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