[clang] [llvm] [clang] Use separator for large numeric values in overflow diagnostic (PR #80939)

[Aaron Ballman via cfe-commits]

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@@ -1626,7 +1626,8 @@ class [[nodiscard]] APInt {
   /// SmallString. If Radix > 10, UpperCase determine the case of letter
   /// digits.
   void toString(SmallVectorImpl<char> &Str, unsigned Radix, bool Signed,
-                bool formatAsCLiteral = false, bool UpperCase = true) const;
+                bool formatAsCLiteral = false, bool UpperCase = true,
+                bool insertSeparators = false) const;
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AaronBallman wrote:

```suggestion
                bool InsertSeparators = false) const;
```
This matches our usual coding style and is the prevailing style in the function signature (a follow-up NFC change could rename `formatAsCLiteral`).

https://github.com/llvm/llvm-project/pull/80939