Fix some inconsistent choices of datatypes in xlog.c.  Make buffer indexes all be int, rather than variously int, uint16 and uint32; add some casts where necessary to support large buffer arrays.
Fix some inconsistent choices of datatypes in xlog.c.  Make buffer
indexes all be int, rather than variously int, uint16 and uint32;
add some casts where necessary to support large buffer arrays.

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