Add doc links from SET to SET_CONSTRAINTS, SET_SESSION_AUTH, SET_TRANSACTION.
Add doc links from SET to SET_CONSTRAINTS, SET_SESSION_AUTH,
SET_TRANSACTION.

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