[ItaniumDemangle] reapply 0e754e1 (#79488)

It got lost in 50b58e8.

Author: nico

libcxxabi/src/demangle/ItaniumDemangle.h

@@ -39,13 +39,12 @@
 DEMANGLE_NAMESPACE_BEGIN
 
 template <class T, size_t N> class PODSmallVector {
-  static_assert(std::is_pod<T>::value,
-                "T is required to be a plain old data type");
-
+  static_assert(std::is_trivial<T>::value,
+                "T is required to be a trivial type");
   T *First = nullptr;
   T *Last = nullptr;
   T *Cap = nullptr;
-  T Inline[N] = {0};
+  T Inline[N] = {};
 
   bool isInline() const { return First == Inline; }
 

llvm/include/llvm/Demangle/ItaniumDemangle.h

@@ -38,13 +38,12 @@
 DEMANGLE_NAMESPACE_BEGIN
 
 template <class T, size_t N> class PODSmallVector {
-  static_assert(std::is_pod<T>::value,
-                "T is required to be a plain old data type");
-
+  static_assert(std::is_trivial<T>::value,
+                "T is required to be a trivial type");
   T *First = nullptr;
   T *Last = nullptr;
   T *Cap = nullptr;
-  T Inline[N] = {0};
+  T Inline[N] = {};
 
   bool isInline() const { return First == Inline; }