f_class(string)</code>: Use the C++ global locale decimal point,
     rather than the C one.
     <br>
     Consider making these variant <code>mpz_set_str</code> etc forms
     available for <code>mpz_t</code> too, not just <code>mpz_class</code>
     etc.
<li> <code>mpq_class operator+=</code>: Don't emit an unnecssary
     <code>mpq_set(q,q)</code> before <code>mpz_addmul</code> etc.
<li> Put various bits of gmpxx.h into libgmpxx, to avoid excessive inlining.
     Candidates for this would be,
     <ul>
