Change a static_assert to check for is_trivial instead of is_pod, as is mandated by P0767.

llvm-svn: 323071
diff --git a/libcxx/include/string b/libcxx/include/string
index f5d5489..b213cd4 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -651,7 +651,7 @@
     typedef typename __alloc_traits::pointer             pointer;
     typedef typename __alloc_traits::const_pointer       const_pointer;
 
-    static_assert(is_pod<value_type>::value, "Character type of basic_string must be a POD");
+    static_assert(is_trivial<value_type>::value, "Character type of basic_string must be trivial");
     static_assert((is_same<_CharT, typename traits_type::char_type>::value),
                   "traits_type::char_type must be the same type as CharT");
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
diff --git a/libcxx/include/string_view b/libcxx/include/string_view
index 72cf816..fd8c379 100644
--- a/libcxx/include/string_view
+++ b/libcxx/include/string_view
@@ -208,7 +208,7 @@
     typedef ptrdiff_t                                  difference_type;
     static _LIBCPP_CONSTEXPR const size_type npos = -1; // size_type(-1);
 
-    static_assert(is_pod<value_type>::value, "Character type of basic_string_view must be a POD");
+    static_assert(is_trivial<value_type>::value, "Character type of basic_string_view must be trivial");
     static_assert((is_same<_CharT, typename traits_type::char_type>::value),
                   "traits_type::char_type must be the same type as CharT");