doc: Document valid checkpoint_timeout range
doc: Document valid checkpoint_timeout range

Author: Fabien COELHO <d1ef580865f8eb2e1d1c65bc406aba322cc98f3e@cri.ensmp.fr>

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