9.3 release notes:  update from Amit Kapila
9.3 release notes:  update from Amit Kapila

No need to mention wal_receiver_status_interval.

ashwinstar/gpdb,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,Postgres-XL/Postgres-XL,adam8157/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,ovr/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,techdragon/Postgres-XL,adam8157/gpdb,zeroae/postgres-xl,xinzweb/gpdb,Postgres-XL/Postgres-XL,yazun/postgres-xl,50wu/gpdb,oberstet/postgres-xl,lisakowen/gpdb,ovr/postgres-xl,ovr/postgres-xl,oberstet/postgres-xl,oberstet/postgres-xl,greenplum-db/gpdb,adam8157/gpdb,ashwinstar/gpdb,ovr/postgres-xl,xinzweb/gpdb,adam8157/gpdb,zeroae/postgres-xl,pavanvd/postgres-xl,greenplum-db/gpdb,xinzweb/gpdb,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,oberstet/postgres-xl,pavanvd/postgres-xl,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,zeroae/postgres-xl,ashwinstar/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,yazun/postgres-xl,50wu/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,xinzweb/gpdb,oberstet/postgres-xl,ovr/postgres-xl,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,lisakowen/gpdb,lisakowen/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,pavanvd/postgres-xl,yazun/postgres-xl,yazun/postgres-xl,50wu/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,yazun/postgres-xl,xinzweb/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb,techdragon/Postgres-XL,xinzweb/gpdb,50wu/gpdb,adam8157/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,50wu/gpdb