[llvm] [llvm][ItaniumDemangle] Use __LDBL_MANT_DIG__ for configuring demangling of long doubles (PR #135968)

[Martin Storsjö via llvm-commits]

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@@ -38,8 +38,10 @@
 DEMANGLE_NAMESPACE_BEGIN
 
 template <class T, size_t N> class PODSmallVector {
-  static_assert(std::is_trivial<T>::value,
-                "T is required to be a trivial type");
+  static_assert(std::is_trivially_copyable<T>::value,
+                "T is required to be a trivially copyable type");
+  static_assert(std::is_trivially_default_constructible<T>::value,
+                "T is required to be trivially default constructible");
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mstorsjo wrote:

Just for the record; these changes here didn't stem from #134976, but from #130573 - the file hasn't been synced after that change.

https://github.com/llvm/llvm-project/pull/135968