Fix typos in exttablecmds.c comments
Fix typos in exttablecmds.c comments

jmcatamney/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,lisakowen/gpdb,greenplum-db/gpdb,xinzweb/gpdb,edespino/gpdb,lisakowen/gpdb,50wu/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,adam8157/gpdb,Quikling/gpdb,adam8157/gpdb,Chibin/gpdb,edespino/gpdb,Quikling/gpdb,50wu/gpdb,Quikling/gpdb,edespino/gpdb,Chibin/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,lintzc/gpdb,rvs/gpdb,cjcjameson/gpdb,adam8157/gpdb,rvs/gpdb,ashwinstar/gpdb,edespino/gpdb,janebeckman/gpdb,adam8157/gpdb,janebeckman/gpdb,ashwinstar/gpdb,Quikling/gpdb,janebeckman/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,50wu/gpdb,Chibin/gpdb,cjcjameson/gpdb,lintzc/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,janebeckman/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,edespino/gpdb,lisakowen/gpdb,janebeckman/gpdb,50wu/gpdb,ashwinstar/gpdb,edespino/gpdb,lisakowen/gpdb,50wu/gpdb,ashwinstar/gpdb,Quikling/gpdb,jmcatamney/gpdb,lintzc/gpdb,janebeckman/gpdb,jmcatamney/gpdb,rvs/gpdb,Chibin/gpdb,lintzc/gpdb,xinzweb/gpdb,xinzweb/gpdb,Quikling/gpdb,ashwinstar/gpdb,adam8157/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,Chibin/gpdb,lintzc/gpdb,edespino/gpdb,kaknikhil/gpdb,rvs/gpdb,greenplum-db/gpdb,xinzweb/gpdb,Quikling/gpdb,kaknikhil/gpdb,kaknikhil/gpdb,janebeckman/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,rvs/gpdb,lisakowen/gpdb,jmcatamney/gpdb,rvs/gpdb,yuanzhao/gpdb,50wu/gpdb,xinzweb/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,adam8157/gpdb,Chibin/gpdb,Chibin/gpdb,jmcatamney/gpdb,Quikling/gpdb,lintzc/gpdb,ashwinstar/gpdb,janebeckman/gpdb,50wu/gpdb,lisakowen/gpdb,rvs/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,janebeckman/gpdb,kaknikhil/gpdb,rvs/gpdb,cjcjameson/gpdb,adam8157/gpdb,xinzweb/gpdb,edespino/gpdb,lintzc/gpdb,yuanzhao/gpdb,Chibin/gpdb,yuanzhao/gpdb,xinzweb/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,rvs/gpdb,Quikling/gpdb,lisakowen/gpdb,Chibin/gpdb,Chibin/gpdb,ashwinstar/gpdb,lintzc/gpdb,lisakowen/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,adam8157/gpdb,jmcatamney/gpdb,Quikling/gpdb,lintzc/gpdb,xinzweb/gpdb,janebeckman/gpdb,rvs/gpdb,edespino/gpdb,50wu/gpdb,edespino/gpdb,yuanzhao/gpdb