From 6469427f972fba89fb88b1230b68f92a91dd4fc6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Tue, 3 Dec 2013 21:21:48 +0100
Subject: [PATCH] Updated std::optional from Optional repository.

---
 external/Optional/optional.hpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/external/Optional/optional.hpp b/external/Optional/optional.hpp
index 55553f3c3..0273a6afd 100644
--- a/external/Optional/optional.hpp
+++ b/external/Optional/optional.hpp
@@ -21,7 +21,11 @@
 # define REQUIRES(...) typename enable_if<__VA_ARGS__::value, bool>::type = false
 
 # if defined __clang__
-#  define OPTIONAL_HAS_USING 1
+#  if (__clang_major__ >= 3)
+#   define OPTIONAL_HAS_USING 1
+#  else
+#   define OPTIONAL_HAS_USING 0
+#  endif
 #  if (__clang_major__ > 2) || (__clang_major__ == 2) && (__clang_minor__ >= 9)
 #   define OPTIONAL_HAS_THIS_RVALUE_REFS 1
 #  else