Feature request #1141: Update to GMP 4.2.4

Cutting and pasting from the release announcement:

Version 4.2.4 of the GNU Multiple Precision Arithmetic Library (GMP) is now
available at:

 ftp://ftp.gnu.org/gnu/gmp/gmp-4.2.4.tar.bz2
 ftp://ftp.gnu.org/gnu/gmp/gmp-4.2.4.tar.gz

These files can also be found on a GNU mirror near you.


The web site for GMP is http://gmplib.org/.

The GMP project is sponsored by CIAM, http://www.ciam.kth.se/, which
is funded by the Swedish Foundation for Strategic Research.

It cannot be said enough times: Please run "make check" after you've built
your library.  And if "make check" stops with an error, do not use the
compiled library.  If this happens, you've almost surely run into a
compiler bug.  The first thing to try is using a different version of the
compiler.  See also http://gmplib.org/.


Changes between GMP version 4.2.3 and 4.2.4

 Bugs:
 * Fix bug with parsing exponent '+' sign in mpf.
 * Fix an allocation bug in mpf_set_str, also affecting mpf_init_set_str, and
   mpf_inp_str.

 Speedups:
 * None, except that proper processor recognition helps affected processors.

 Features:
 * Recognize new AMD processors.

Torbjörn Granlund