Clarify documentation of age() functions.
Clarify documentation of age() functions.

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