[utils/ularith.h] avoid warning when sizeof(long) == 32
[utils/ularith.h] avoid warning when sizeof(long) == 32

mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs