[clang] modified AST for SEI redemption project (PR #111705)

[Aaron Ballman via cfe-commits]

================
@@ -132,6 +151,9 @@ class JSONNodeDumper
   StringRef LastLocFilename, LastLocPresumedFilename;
   unsigned LastLocLine, LastLocPresumedLine;
 
+  // SEI: caches addresses for QualType nodes that are duplicates
+  std::unordered_set<void *> AddressCache;
----------------
AaronBallman wrote:

```suggestion
  // Caches addresses for QualType nodes that are duplicates
  llvm::DenseSet<void *> AddressCache;
```

https://github.com/llvm/llvm-project/pull/111705