libgmp: Update from version 5.0.2 to 5.0.5

libgmp: Update from version 5.0.2 to 5.0.5

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 CHANGES SINCE PREVIOUS UPDATE
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Changes between GMP version 5.0.2 and 5.0.3
[BUGS FIXED]
* A few minor bugs related to portability fixed.
* A slight timing leak of the powm_sec functions have been sealed.
  (This leak could possibly be used to extract the most significant
  few bits of the exponent.  "Few" here means at most 10.)
* The mpz_nextprime function now runs a safer number of pseudo-random
  prime tests.
* A bug in division code possibly causing incorrect computation was
  fixed.
[SPEEDUPS]
* None, except indirectly through recognition of new CPUs, and through
  better tuning parameters.
[FEATURES]
* New CPUs recognised.
* IBM S/390 are now supported in both 31/32-bit and 64-bit mode.  (We
  have not been able to fully test this on any multilib machine, since
  IBM expired our guest account a few days before our release.)

Changes between GMP version 5.0.3 and 5.0.4
[BUGS FIXED]
* Thresholds in mpn_powm_sec for both fat and non-fat builds are now
  used safely, plugging a one-word buffer overrun introduced in the
  5.0.3 release (for non-fat) and a multi-word buffer overrun that
  existed since 5.0 (for fat).  (We have not been able to provoke malign
  stack smashing in any of the ~100 configurations explored by the GMP
  nightly builds, but the bug should be assumed to be exploitable.)
* Two bugs in multiplication code causing incorrect computation with
  extremely low probability have been fixed.
* A bug in the test suite causing buffer overruns during "make check",
  sometimes leading to subsequent malloc crashes, has been fixed.
* Two bugs in the gcd code have been fixed.  They could lead to incorrect
  results, but for uniformly distributed random operands, the likelihood
  for that is infinitesimally small.  (There was also a third bug, but
  that was an incorrect ASSERT, which furthermore was not enabled by
  default.)
* A bug affecting 32-bit PowerPC division has been fixed.  The bug caused
  miscomputation for certain divisors in the range 2^32 ... 2^64-1
  (about 1 in 2^30 of these).
[SPEEDUPS]
* None, except indirectly through recognition of new CPUs, and through
  better tuning parameters.
[FEATURES]
* Some more tests added to the self-check suite.
* The AMD "Bulldozer" CPU is now recognised.

Changes between GMP version 5.0.4 and 5.0.5
[BUGS FIXED]
* A bug causing AMD 11h processors to be treated like AMD 10h has been
  fixed.  The 11h processors do not correctly handle all 10h (aka K10)
  instructions, and GMP's use of these instructions results in major
  miscomputations (not as one would have hoped CPU traps of some
  'illegal instruction' sort).
* A bug affecting recent Intel Sandy Bridge CPUs resulting in
  configuration failures has been fixed,
[FEATURES]
* A couple of tests added to the self-check suite.