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

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@323071 91177308-0d34-0410-b5e6-96231b3b80d8

include/string

@@ -651,7 +651,7 @@ public:
     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),

include/string_view

@@ -208,7 +208,7 @@ public:
     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");