Add release notes for back branches (7.3 and up). Also minor improvements to 8.1.1 release notes.
Add release notes for back branches (7.3 and up).
Also minor improvements to 8.1.1 release notes.

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