Correct some comments, fix a small memory wastage when datatype is pass-by-value.
Correct some comments, fix a small memory wastage when datatype
is pass-by-value.

kaknikhil/gpdb,lintzc/gpdb,greenplum-db/gpdb,xinzweb/gpdb,atris/gpdb,rubikloud/gpdb,lintzc/gpdb,foyzur/gpdb,edespino/gpdb,zaksoup/gpdb,adam8157/gpdb,zeroae/postgres-xl,yuanzhao/gpdb,tangp3/gpdb,arcivanov/postgres-xl,lisakowen/gpdb,tangp3/gpdb,tpostgres-projects/tPostgres,greenplum-db/gpdb,janebeckman/gpdb,ahachete/gpdb,edespino/gpdb,zaksoup/gpdb,cjcjameson/gpdb,atris/gpdb,Postgres-XL/Postgres-XL,Postgres-XL/Postgres-XL,atris/gpdb,0x0FFF/gpdb,tangp3/gpdb,zeroae/postgres-xl,chrishajas/gpdb,yuanzhao/gpdb,chrishajas/gpdb,kmjungersen/PostgresXL,CraigHarris/gpdb,cjcjameson/gpdb,janebeckman/gpdb,50wu/gpdb,janebeckman/gpdb,janebeckman/gpdb,randomtask1155/gpdb,cjcjameson/gpdb,techdragon/Postgres-XL,arcivanov/postgres-xl,yuanzhao/gpdb,rubikloud/gpdb,jmcatamney/gpdb,rvs/gpdb,rvs/gpdb,adam8157/gpdb,kaknikhil/gpdb,Quikling/gpdb,xinzweb/gpdb,xuegang/gpdb,Postgres-XL/Postgres-XL,chrishajas/gpdb,Chibin/gpdb,yazun/postgres-xl,techdragon/Postgres-XL,CraigHarris/gpdb,rvs/gpdb,janebeckman/gpdb,Chibin/gpdb,xinzweb/gpdb,xinzweb/gpdb,royc1/gpdb,atris/gpdb,ahachete/gpdb,postmind-net/postgres-xl,cjcjameson/gpdb,royc1/gpdb,50wu/gpdb,adam8157/gpdb,0x0FFF/gpdb,postmind-net/postgres-xl,foyzur/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,randomtask1155/gpdb,oberstet/postgres-xl,rubikloud/gpdb,cjcjameson/gpdb,yuanzhao/gpdb,foyzur/gpdb,chrishajas/gpdb,ahachete/gpdb,edespino/gpdb,Chibin/gpdb,kaknikhil/gpdb,janebeckman/gpdb,yazun/postgres-xl,jmcatamney/gpdb,lpetrov-pivotal/gpdb,arcivanov/postgres-xl,tangp3/gpdb,zaksoup/gpdb,tpostgres-projects/tPostgres,adam8157/gpdb,yuanzhao/gpdb,edespino/gpdb,foyzur/gpdb,postmind-net/postgres-xl,royc1/gpdb,lisakowen/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,yuanzhao/gpdb,randomtask1155/gpdb,50wu/gpdb,tangp3/gpdb,0x0FFF/gpdb,rvs/gpdb,oberstet/postgres-xl,ovr/postgres-xl,Quikling/gpdb,xuegang/gpdb,kaknikhil/gpdb,CraigHarris/gpdb,ahachete/gpdb,zeroae/postgres-xl,randomtask1155/gpdb,lintzc/gpdb,greenplum-db/gpdb,lpetrov-pivotal/gpdb,techdragon/Postgres-XL,xuegang/gpdb,Quikling/gpdb,ahachete/gpdb,Quikling/gpdb,Chibin/gpdb,Chibin/gpdb,greenplum-db/gpdb,ovr/postgres-xl,atris/gpdb,Postgres-XL/Postgres-XL,postmind-net/postgres-xl,yuanzhao/gpdb,edespino/gpdb,adam8157/gpdb,lintzc/gpdb,lpetrov-pivotal/gpdb,ovr/postgres-xl,rvs/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,adam8157/gpdb,xinzweb/gpdb,atris/gpdb,Chibin/gpdb,ovr/postgres-xl,Quikling/gpdb,tpostgres-projects/tPostgres,snaga/postgres-xl,postmind-net/postgres-xl,atris/gpdb,xuegang/gpdb,Quikling/gpdb,jmcatamney/gpdb,arcivanov/postgres-xl,lisakowen/gpdb,ashwinstar/gpdb,zaksoup/gpdb,0x0FFF/gpdb,xuegang/gpdb,atris/gpdb,chrishajas/gpdb,arcivanov/postgres-xl,yuanzhao/gpdb,lpetrov-pivotal/gpdb,Quikling/gpdb,oberstet/postgres-xl,lisakowen/gpdb,tangp3/gpdb,zaksoup/gpdb,ashwinstar/gpdb,lintzc/gpdb,tangp3/gpdb,CraigHarris/gpdb,0x0FFF/gpdb,janebeckman/gpdb,foyzur/gpdb,jmcatamney/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,lpetrov-pivotal/gpdb,janebeckman/gpdb,xinzweb/gpdb,foyzur/gpdb,zeroae/postgres-xl,ahachete/gpdb,0x0FFF/gpdb,ovr/postgres-xl,xuegang/gpdb,arcivanov/postgres-xl,rvs/gpdb,50wu/gpdb,zaksoup/gpdb,Quikling/gpdb,yazun/postgres-xl,pavanvd/postgres-xl,chrishajas/gpdb,techdragon/Postgres-XL,lpetrov-pivotal/gpdb,lintzc/gpdb,tpostgres-projects/tPostgres,ashwinstar/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,kaknikhil/gpdb,adam8157/gpdb,Quikling/gpdb,tpostgres-projects/tPostgres,edespino/gpdb,Quikling/gpdb,rubikloud/gpdb,cjcjameson/gpdb,lintzc/gpdb,kaknikhil/gpdb,xinzweb/gpdb,rvs/gpdb,kaknikhil/gpdb,foyzur/gpdb,cjcjameson/gpdb,rubikloud/gpdb,ashwinstar/gpdb,xinzweb/gpdb,xuegang/gpdb,kmjungersen/PostgresXL,edespino/gpdb,snaga/postgres-xl,lisakowen/gpdb,royc1/gpdb,randomtask1155/gpdb,lpetrov-pivotal/gpdb,randomtask1155/gpdb,xuegang/gpdb,50wu/gpdb,randomtask1155/gpdb,ashwinstar/gpdb,edespino/gpdb,royc1/gpdb,zaksoup/gpdb,snaga/postgres-xl,Chibin/gpdb,yuanzhao/gpdb,chrishajas/gpdb,snaga/postgres-xl,kaknikhil/gpdb,janebeckman/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,CraigHarris/gpdb,lisakowen/gpdb,royc1/gpdb,lintzc/gpdb,rubikloud/gpdb,CraigHarris/gpdb,yazun/postgres-xl,rvs/gpdb,zaksoup/gpdb,oberstet/postgres-xl,rvs/gpdb,oberstet/postgres-xl,50wu/gpdb,kmjungersen/PostgresXL,edespino/gpdb,chrishajas/gpdb,royc1/gpdb,rubikloud/gpdb,greenplum-db/gpdb,rubikloud/gpdb,ahachete/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,lpetrov-pivotal/gpdb,Chibin/gpdb,techdragon/Postgres-XL,kaknikhil/gpdb,foyzur/gpdb,greenplum-db/gpdb,snaga/postgres-xl,pavanvd/postgres-xl,50wu/gpdb,royc1/gpdb,edespino/gpdb,lintzc/gpdb,kmjungersen/PostgresXL,ashwinstar/gpdb,lisakowen/gpdb,kmjungersen/PostgresXL,Chibin/gpdb,yazun/postgres-xl,50wu/gpdb,jmcatamney/gpdb,Chibin/gpdb,kaknikhil/gpdb,janebeckman/gpdb,xuegang/gpdb,randomtask1155/gpdb,cjcjameson/gpdb,tangp3/gpdb,zeroae/postgres-xl,ahachete/gpdb,rvs/gpdb,adam8157/gpdb,cjcjameson/gpdb,CraigHarris/gpdb,greenplum-db/gpdb