Made printing of special FP values portable.

src/ostreams.cc

Index: src/ostreams.cc
diff --git a/src/ostreams.cc b/src/ostreams.cc
index b04803cf9f6e77fc0589ee235f0cd57aa277bc96..cf4b9d5d60d2a227ee65a4b584db65189f10fb79 100644
--- a/src/ostreams.cc
+++ b/src/ostreams.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include <algorithm>
+#include <cmath>
 
 #include "src/ostreams.h"
 
@@ -63,6 +64,8 @@ OStream& OStream::operator<<(unsigned long long x) {  // NOLINT(runtime/int)
 
 
 OStream& OStream::operator<<(double x) {
+  if (std::isinf(x)) return *this << (x < 0 ? "-inf" : "inf");
+  if (std::isnan(x)) return *this << "nan";
   return print("%g", x);
 }