[llvm] [ADT] Add `isPunct` to StringExtras (PR #105461)

[Yanzuo Liu via llvm-commits]

================
@@ -380,3 +382,14 @@ TEST(StringExtrasTest, arrayToStringRef) {
   roundTripTestString("\0\n");
   roundTripTestString("\xFF\xFE");
 }
+
+TEST(StringExtrasTest, isPunct) {
+  // Loop over all valid char values and verify that llvm::isPunct matched
+  // std::ispunct(). Limit to first 256 characters in case sizeof(char) > 8.
----------------
zwuis wrote:

```suggestion
  // std::ispunct(). Limit to first 256 characters in case CHAR_BIT > 8.
```


https://github.com/llvm/llvm-project/pull/105461