increase number of curves from 20 to 24 (better for 33-bit primes)
increase number of curves from 20 to 24 (better for 33-bit primes)

Maybe we could set NB_CURVES according to lpb[ra]?

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