Fixed d8 on leopard.

src/platform-freebsd.cc

Index: src/platform-freebsd.cc
diff --git a/src/platform-freebsd.cc b/src/platform-freebsd.cc
index 75140c99850860ad43696688c7fe5c493cf9e3ed..d7b3223a49139354263e6a847ab6ba84b6493de2 100644
--- a/src/platform-freebsd.cc
+++ b/src/platform-freebsd.cc
@@ -194,6 +194,11 @@ char *OS::StrDup(const char* str) {
 }
 
 
+char* OS::StrNDup(const char* str, size_t n) {
+  return strndup(str, n);
+}
+
+
 double OS::nan_value() {
   return NAN;
 }