 be a rather big inline, or would have
          to be two function calls.
     <li> <code>mpz_get_sll</code> would be a worse inline, and would put the
          treatment of <code>-0x10..00</code> into applications (see
          <code>mpz_get_si</code> correctness above).
     <li> Although having libgmp.a independent of the build compiler is nice,
          it sort of sacrifices the capabilities of a good compiler to
          uniformity with inferior ones.
     </ul>
     Plain use of <code>long long</