The mpfr functions have been removed from the public GMP 4.0
release.  This was made since paperwork was not ready in
time for the release.  The mpfr developers also wanted to
address some known issues, before a new mpfr is released
with GMP.

While we could have kept the old mpfr code that was included
with GMP 3, the mpfr developers felt that that code is
obsolete.

If you need to use the mpfr functions now, please see:
<http://www.mpfr.org/>.

We expect that the next GMP release (4.1) or a possible
patch release (4.0.1) will again include mpfr.
