Remove deprecated v8::base::OS::nan_value().

src/base/platform/platform-posix.cc

Index: src/base/platform/platform-posix.cc
diff --git a/src/base/platform/platform-posix.cc b/src/base/platform/platform-posix.cc
index ebf7261245d700ba1b6789c8bc2e9c60b6b6f1ef..5393dd57c9563545991e76e5d58960b0f4a5c888 100644
--- a/src/base/platform/platform-posix.cc
+++ b/src/base/platform/platform-posix.cc
@@ -249,15 +249,6 @@ void OS::DebugBreak() {
 }
 
 
-// ----------------------------------------------------------------------------
-// Math functions
-
-double OS::nan_value() {
-  // NAN from math.h is defined in C99 and not in POSIX.
-  return NAN;
-}
-
-
 int OS::GetCurrentProcessId() {
   return static_cast<int>(getpid());
 }
@@ -319,10 +310,10 @@ void OS::ClearTimezoneCache(TimezoneCache* cache) {
 
 
 double OS::DaylightSavingsOffset(double time, TimezoneCache*) {
-  if (std::isnan(time)) return nan_value();
+  if (std::isnan(time)) return std::numeric_limits<double>::quiet_NaN();
   time_t tv = static_cast<time_t>(std::floor(time/msPerSecond));
   struct tm* t = localtime(&tv);
-  if (NULL == t) return nan_value();
+  if (NULL == t) return std::numeric_limits<double>::quiet_NaN();
   return t->tm_isdst > 0 ? 3600 * msPerSecond : 0;
 }