Add example for pg_config --configure.
Add example for pg_config --configure.

randomtask1155/gpdb,tangp3/gpdb,CraigHarris/gpdb,lintzc/gpdb,yuanzhao/gpdb,tpostgres-projects/tPostgres,pavanvd/postgres-xl,lisakowen/gpdb,pavanvd/postgres-xl,edespino/gpdb,ahachete/gpdb,ahachete/gpdb,xuegang/gpdb,techdragon/Postgres-XL,postmind-net/postgres-xl,atris/gpdb,zaksoup/gpdb,janebeckman/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,chrishajas/gpdb,cjcjameson/gpdb,chrishajas/gpdb,adam8157/gpdb,50wu/gpdb,lpetrov-pivotal/gpdb,rvs/gpdb,royc1/gpdb,lisakowen/gpdb,Chibin/gpdb,rubikloud/gpdb,tangp3/gpdb,CraigHarris/gpdb,atris/gpdb,xinzweb/gpdb,atris/gpdb,edespino/gpdb,janebeckman/gpdb,lisakowen/gpdb,50wu/gpdb,CraigHarris/gpdb,lisakowen/gpdb,jmcatamney/gpdb,xuegang/gpdb,Quikling/gpdb,jmcatamney/gpdb,lpetrov-pivotal/gpdb,50wu/gpdb,xinzweb/gpdb,rvs/gpdb,cjcjameson/gpdb,rvs/gpdb,edespino/gpdb,tangp3/gpdb,ahachete/gpdb,ahachete/gpdb,cjcjameson/gpdb,rubikloud/gpdb,rubikloud/gpdb,techdragon/Postgres-XL,lintzc/gpdb,greenplum-db/gpdb,Chibin/gpdb,Chibin/gpdb,rvs/gpdb,50wu/gpdb,edespino/gpdb,Quikling/gpdb,jmcatamney/gpdb,yazun/postgres-xl,techdragon/Postgres-XL,kmjungersen/PostgresXL,ashwinstar/gpdb,adam8157/gpdb,kaknikhil/gpdb,tpostgres-projects/tPostgres,rubikloud/gpdb,xinzweb/gpdb,50wu/gpdb,rubikloud/gpdb,atris/gpdb,oberstet/postgres-xl,rvs/gpdb,kmjungersen/PostgresXL,kaknikhil/gpdb,randomtask1155/gpdb,postmind-net/postgres-xl,CraigHarris/gpdb,royc1/gpdb,ahachete/gpdb,cjcjameson/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,randomtask1155/gpdb,ahachete/gpdb,Chibin/gpdb,ovr/postgres-xl,kaknikhil/gpdb,lpetrov-pivotal/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,lintzc/gpdb,kaknikhil/gpdb,adam8157/gpdb,chrishajas/gpdb,xuegang/gpdb,techdragon/Postgres-XL,yazun/postgres-xl,xinzweb/gpdb,foyzur/gpdb,tangp3/gpdb,rvs/gpdb,zaksoup/gpdb,kaknikhil/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,janebeckman/gpdb,Postgres-XL/Postgres-XL,yuanzhao/gpdb,Chibin/gpdb,rvs/gpdb,Chibin/gpdb,cjcjameson/gpdb,ashwinstar/gpdb,foyzur/gpdb,Quikling/gpdb,randomtask1155/gpdb,ashwinstar/gpdb,royc1/gpdb,rubikloud/gpdb,yuanzhao/gpdb,tpostgres-projects/tPostgres,kmjungersen/PostgresXL,greenplum-db/gpdb,CraigHarris/gpdb,chrishajas/gpdb,zaksoup/gpdb,lpetrov-pivotal/gpdb,janebeckman/gpdb,xinzweb/gpdb,rvs/gpdb,chrishajas/gpdb,edespino/gpdb,Quikling/gpdb,CraigHarris/gpdb,lintzc/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,yuanzhao/gpdb,tangp3/gpdb,postmind-net/postgres-xl,zeroae/postgres-xl,lpetrov-pivotal/gpdb,xuegang/gpdb,Postgres-XL/Postgres-XL,kaknikhil/gpdb,yazun/postgres-xl,Postgres-XL/Postgres-XL,jmcatamney/gpdb,arcivanov/postgres-xl,kaknikhil/gpdb,zeroae/postgres-xl,atris/gpdb,0x0FFF/gpdb,janebeckman/gpdb,lintzc/gpdb,pavanvd/postgres-xl,royc1/gpdb,snaga/postgres-xl,lpetrov-pivotal/gpdb,arcivanov/postgres-xl,chrishajas/gpdb,ahachete/gpdb,royc1/gpdb,oberstet/postgres-xl,greenplum-db/gpdb,yuanzhao/gpdb,tangp3/gpdb,Chibin/gpdb,janebeckman/gpdb,Chibin/gpdb,0x0FFF/gpdb,cjcjameson/gpdb,xuegang/gpdb,zeroae/postgres-xl,zaksoup/gpdb,yazun/postgres-xl,snaga/postgres-xl,zaksoup/gpdb,Quikling/gpdb,Quikling/gpdb,yuanzhao/gpdb,Chibin/gpdb,adam8157/gpdb,CraigHarris/gpdb,ovr/postgres-xl,lintzc/gpdb,greenplum-db/gpdb,snaga/postgres-xl,janebeckman/gpdb,kaknikhil/gpdb,Chibin/gpdb,rvs/gpdb,edespino/gpdb,edespino/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,royc1/gpdb,0x0FFF/gpdb,randomtask1155/gpdb,postmind-net/postgres-xl,janebeckman/gpdb,tpostgres-projects/tPostgres,greenplum-db/gpdb,postmind-net/postgres-xl,0x0FFF/gpdb,xuegang/gpdb,foyzur/gpdb,rvs/gpdb,Quikling/gpdb,Quikling/gpdb,CraigHarris/gpdb,atris/gpdb,lpetrov-pivotal/gpdb,techdragon/Postgres-XL,foyzur/gpdb,xinzweb/gpdb,lintzc/gpdb,ashwinstar/gpdb,lintzc/gpdb,foyzur/gpdb,kmjungersen/PostgresXL,zeroae/postgres-xl,zeroae/postgres-xl,foyzur/gpdb,ovr/postgres-xl,0x0FFF/gpdb,lintzc/gpdb,0x0FFF/gpdb,foyzur/gpdb,arcivanov/postgres-xl,adam8157/gpdb,ovr/postgres-xl,atris/gpdb,zaksoup/gpdb,adam8157/gpdb,ashwinstar/gpdb,kaknikhil/gpdb,Quikling/gpdb,snaga/postgres-xl,adam8157/gpdb,yazun/postgres-xl,Quikling/gpdb,50wu/gpdb,tangp3/gpdb,ovr/postgres-xl,yuanzhao/gpdb,tangp3/gpdb,jmcatamney/gpdb,lpetrov-pivotal/gpdb,arcivanov/postgres-xl,xinzweb/gpdb,50wu/gpdb,snaga/postgres-xl,janebeckman/gpdb,adam8157/gpdb,cjcjameson/gpdb,rubikloud/gpdb,chrishajas/gpdb,oberstet/postgres-xl,tpostgres-projects/tPostgres,arcivanov/postgres-xl,0x0FFF/gpdb,rubikloud/gpdb,xuegang/gpdb,randomtask1155/gpdb,pavanvd/postgres-xl,cjcjameson/gpdb,xuegang/gpdb,xinzweb/gpdb,edespino/gpdb,kmjungersen/PostgresXL,zaksoup/gpdb,atris/gpdb,arcivanov/postgres-xl,lisakowen/gpdb,0x0FFF/gpdb,royc1/gpdb,CraigHarris/gpdb,janebeckman/gpdb,randomtask1155/gpdb,foyzur/gpdb,chrishajas/gpdb,zaksoup/gpdb,ahachete/gpdb,oberstet/postgres-xl,edespino/gpdb,edespino/gpdb,randomtask1155/gpdb,yuanzhao/gpdb,oberstet/postgres-xl,greenplum-db/gpdb,kaknikhil/gpdb,lisakowen/gpdb,royc1/gpdb,lisakowen/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,xuegang/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,jmcatamney/gpdb