[mpz_poly.cpp] fixed Chung-Hasan function (now default for degree 2 squaring)
[mpz_poly.cpp] fixed Chung-Hasan function (now default for degree 2 squaring)

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