Give a better error message when trying to change "effective_io_concurrency" on systems without posix_fadvise().
Give a better error message when trying to change
"effective_io_concurrency" on systems without posix_fadvise().

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