[clang] [clang] Support 'this' position for lifetimebound attribute (PR #115021)

[Saleem Abdulrasool via cfe-commits]

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@@ -516,7 +524,17 @@ class CXXMethodTableInfo
   static CXXMethodInfo readUnversioned(internal_key_type Key,
                                        const uint8_t *&Data) {
     CXXMethodInfo Info;
+
+    uint8_t Payload = *Data++;
+    bool HasThis = Payload & 0x01;
+    Payload >>= 1;
+    assert(Payload == 0 && "Wrong format.");
----------------
compnerd wrote:

```suggestion
    assert(Payload == 0 && "Unable to fully decode 'Payload'.");
```

https://github.com/llvm/llvm-project/pull/115021