_padic_radix_poly_mulmid_packed, _padic_radix_poly_mulmid, _padic_radix_poly_mullow

Set res to the coefficients $n_{lo}, \ldots, n_{hi} - 1$ (respectively $0, \ldots, n - 1$) of the product of the polynomials. Coefficients that are a single product are computed with padic_radix_mul. The unpacked versions implement the generic methods. For both lengths at least 4, from an estimate $S$ of the output windows in limbs (the size of the units, plus one if the valuations are not multiples of $e$, plus the spread of the limb frames): the mod version when $S = 1$; for $S = 2$ from a length of about 64, for $S \le 10$ from about 24, and the radix KS version for $S > 10$ from about 32 (these crossovers raised when the frames are spread out); the packed version otherwise. Before choosing a Kronecker substitution route when the frames are spread out, the windows of 16 sampled outputs are estimated from the context precision, and the packed version is used if the base frames inflate at least three of them as above; if a route still gives up, the packed version is used without trying the other. Shorter products use the classical algorithm.