Update valgrind.h to newer version.

Committed http://code.google.com/p/v8/source/detail?r=8721

Update valgrind.h to newer version.

* src/third_party/valgrind/valgrind.h: Update from upstream valgrind
  r11899, so as to get around some unused value warnings. Also adds
  support for darwin.

  This version of valgrind.h differs from the original in that all
  instances of "unsigned long long int" have been replaced with
  "uint64_t", as the former is not allowed in ISO C++ 89.

  See https://bugs.kde.org/show_bug.cgi?id=211926 for the upstream bug
  report.

  This version of valgrind.h is slightly newer than the one in Chrome's
  base/third_party, which is in turn newer than the existing V8
  valgrind.h.  Chrome's version doesn't have the needed warning fix.

* src/x64/cpu-x64.cc: Mark the result of VALGRIND_DISCARD_TRANSLATIONS
  as used.

See also http://codereview.chromium.org/7400023/.

[wingo, 2011-07-20 16:30:13]

Here's the valgrind bits split out from http://codereview.chromium.org/7400023/.

[William Hesse, 2011-07-21 08:56:43]

LGTM.  I will do a Valgrind run before committing it.