Add additional example for interval multiplication.
Add additional example for interval multiplication.

Fix example for day and hours interval subtraction for new computation
method.

Update interval examples to display zero seconds, which is our default.

Backpatch to 8.1.X.

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