Make sure [at_]quick_exit is in std::



git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@152717 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__config b/include/__config
index e0b9582..6b29014 100644
--- a/include/__config
+++ b/include/__config
@@ -245,6 +245,10 @@
 #define _LIBCPP_HAS_NO_CONSTEXPR
 #endif
 
+#if __FreeBSD__
+#define _LIBCPP_HAS_QUICK_EXIT
+#endif
+
 #if (__has_feature(cxx_noexcept))
 #  define _NOEXCEPT noexcept
 #  define _NOEXCEPT_(x) noexcept(x)