Generalize width_bucket() documentation because b1/b2 can be interchanged.
Generalize width_bucket() documentation because b1/b2 can be
interchanged.

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