pg_resetxlog: handle platform support for uint64 parsing
pg_resetxlog: handle platform support for uint64 parsing

For 8-byte-long platforms, strtoul() is fine. Otherwise we try to use
strtoull(), and then fail to compile if that doesn't exist.

Co-authored-by: Jim Doty <1edafe41f7177ae695a4a212e0a903db6d46d401@pivotal.io>

greenplum-db/gpdb,lisakowen/gpdb,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,jmcatamney/gpdb,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,50wu/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,ashwinstar/gpdb,xinzweb/gpdb,greenplum-db/gpdb,lisakowen/gpdb,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb