Remove unused code from fmpz_poly_pow_binexp
Remove unused code from fmpz_poly_pow_binexp

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