Fixed the int64_t gmp proxies for 32-bits.
Fixed the int64_t gmp proxies for 32-bits.

using mpz_div_2exp on potentially signed values is dangerous and can lead
to unexpected results !

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