nails cxx error

[Torbjorn Granlund]

Torbjorn Granlund <tg at swox.com> writes:

  A patch is at <http://gmplib.org/#STATUS>.
  
I now realize that my patch doesn't fully solve the problem.  mpf_eq
might still involve too many bits in the comparison.

To get things tight, one needs to locate the position of the most
significant bit of the operands, and count bits downwards from there.

The patched function is at least somewhat better than the original.
:-)

I'll address this properly for GMP 4.3.

-- 
Torbjörn