Fix typo in comment.
Fix typo in comment.

extent -> extend. And reformat.

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