Put back our old workaround for machines that declare cbrt() in math.h but fail to provide the function itself.  Not sure how we escaped testing anything later than 7.3 on such cases, but they still exist, as per André Volpato's report about AIX 5.3.
Put back our old workaround for machines that declare cbrt() in math.h but
fail to provide the function itself.  Not sure how we escaped testing anything
later than 7.3 on such cases, but they still exist, as per André Volpato's
report about AIX 5.3.

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