Further improvement to fmpz_poly_compose_divconquer, plus space analysis
Further improvement to fmpz_poly_compose_divconquer, plus space analysis

dsroche/flint2,dsroche/flint2,wbhart/flint2,fredrik-johansson/flint2,wbhart/flint2,jpflori/flint2,dsroche/flint2,jpflori/flint2,wbhart/flint2,fredrik-johansson/flint2,fredrik-johansson/flint2,jpflori/flint2,jpflori/flint2,dsroche/flint2