pg_upgrade broken by xlog numbering

On HEAD at the moment, `make check-world` is failing on a 32-bit Linux
build:

+ pg_upgrade -d
/home/kevin/pg/master/contrib/pg_upgrade/tmp_check/data.old -D
/home/kevin/pg/master/contrib/pg_upgrade/tmp_check/data -b
/home/kevin/pg/master/contrib/pg_upgrade/tmp_check/install//home/kevin/pg/master/Debug/bin
-B
/home/kevin/pg/master/contrib/pg_upgrade/tmp_check/install//home/kevin/pg/master/Debug/bin
Performing Consistency Checks
-----------------------------
Checking current, bin, and data directories                 ok
Checking cluster versions                                   ok
Some required control information is missing;  cannot find: first log file ID after reset first log file segment after
reset

Cannot continue without required control information, terminating
Failure, exiting