Fix buffer overrun in to_ascii(), per report from Guido Notari.
Fix buffer overrun in to_ascii(), per report from Guido Notari.

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