Add support for AT TIME ZONE syntax.
Add support for AT TIME ZONE syntax.

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