Add missing include in <numeric>

llvm-svn: 294393
diff --git a/libcxx/include/numeric b/libcxx/include/numeric
index e005808..ff2853e 100644
--- a/libcxx/include/numeric
+++ b/libcxx/include/numeric
@@ -65,6 +65,7 @@
 
 #include <__config>
 #include <iterator>
+#include <limits> // for numeric_limits
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header