SFINAE out duration converting constructor if the constructor would otherwise cause a ratio compile-time overflow. This fixes LWG 2094.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@189722 91177308-0d34-0410-b5e6-96231b3b80d8

test/utilities/time/time.point/time.point.cast/time_point_cast.pass.cpp

@@ -35,6 +35,8 @@ test(const FromDuration& df, const ToDuration& d)
     }
 }
 
+#if _LIBCPP_STD_VER > 11
+
 template<class FromDuration, long long From, class ToDuration, long long To>
 void test_constexpr ()
 {
@@ -49,6 +51,8 @@ void test_constexpr ()
 
 }
 
+#endif
+
 int main()
 {
     test(std::chrono::milliseconds(7265000), std::chrono::hours(2));