Implement std::string_view as described in http://wg21.link/P0254R1. Reviewed as https://reviews.llvm.org/D21459

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276238 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/ostream b/include/ostream
index f55fd40..58a4768 100644
--- a/include/ostream
+++ b/include/ostream
@@ -1080,6 +1080,14 @@
     return _VSTD::__put_character_sequence(__os, __str.data(), __str.size());
 }
 
+template<class _CharT, class _Traits>
+basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits>& __os,
+           const basic_string_view<_CharT, _Traits> __sv)
+{
+    return _VSTD::__put_character_sequence(__os, __sv.data(), __sv.size());
+}
+
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>&