Update release notes for 9.0 beta 4.  Back-patch some changes that were made only in HEAD.
Update release notes for 9.0 beta 4.  Back-patch some changes that were made only in HEAD.

ovr/postgres-xl,jmcatamney/gpdb,tpostgres-projects/tPostgres,adam8157/gpdb,Postgres-XL/Postgres-XL,kmjungersen/PostgresXL,xinzweb/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,xinzweb/gpdb,greenplum-db/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,adam8157/gpdb,zeroae/postgres-xl,lisakowen/gpdb,50wu/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,techdragon/Postgres-XL,ashwinstar/gpdb,jmcatamney/gpdb,xinzweb/gpdb,yazun/postgres-xl,postmind-net/postgres-xl,greenplum-db/gpdb,kmjungersen/PostgresXL,techdragon/Postgres-XL,zeroae/postgres-xl,ovr/postgres-xl,zeroae/postgres-xl,ovr/postgres-xl,pavanvd/postgres-xl,lisakowen/gpdb,ovr/postgres-xl,techdragon/Postgres-XL,greenplum-db/gpdb,adam8157/gpdb,arcivanov/postgres-xl,tpostgres-projects/tPostgres,adam8157/gpdb,Postgres-XL/Postgres-XL,yazun/postgres-xl,arcivanov/postgres-xl,snaga/postgres-xl,greenplum-db/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,adam8157/gpdb,yazun/postgres-xl,postmind-net/postgres-xl,50wu/gpdb,ashwinstar/gpdb,lisakowen/gpdb,tpostgres-projects/tPostgres,pavanvd/postgres-xl,jmcatamney/gpdb,50wu/gpdb,yazun/postgres-xl,techdragon/Postgres-XL,yazun/postgres-xl,ashwinstar/gpdb,kmjungersen/PostgresXL,tpostgres-projects/tPostgres,postmind-net/postgres-xl,lisakowen/gpdb,50wu/gpdb,greenplum-db/gpdb,snaga/postgres-xl,ashwinstar/gpdb,50wu/gpdb,arcivanov/postgres-xl,jmcatamney/gpdb,arcivanov/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,50wu/gpdb,snaga/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,kmjungersen/PostgresXL,postmind-net/postgres-xl,zeroae/postgres-xl,Postgres-XL/Postgres-XL,jmcatamney/gpdb,tpostgres-projects/tPostgres,lisakowen/gpdb,oberstet/postgres-xl,postmind-net/postgres-xl,snaga/postgres-xl,kmjungersen/PostgresXL,arcivanov/postgres-xl,lisakowen/gpdb,50wu/gpdb,oberstet/postgres-xl,Postgres-XL/Postgres-XL,xinzweb/gpdb,ovr/postgres-xl,snaga/postgres-xl,oberstet/postgres-xl,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,arcivanov/postgres-xl,greenplum-db/gpdb,xinzweb/gpdb