itly 16.  They currently only allow that prefix when the base is
     unspecified (zero).
<li> <code>mpf_eq</code> is not always correct, when one operand is
     1000000000... and the other operand is 0111111111..., i.e., extremely
     close.  There is a special case in <code>mpf_sub</code> for this
     situation; put similar code in <code>mpf_eq</code>.  [In progress.]
<li> <code>mpf_eq</code> doesn't implement what gmp.texi specifies.  It should
     not use just whole limbs, but partial limbs.  [In pr