[clang] [clang] Accept empty enum in MSVC compatible C (PR #159981)

[Aaron Ballman via cfe-commits]

================
@@ -2406,6 +2406,16 @@ those modes.
 Use ``__has_feature(c_fixed_enum)`` to determine whether support for fixed
 underlying types is available in C23 and later.
 
+Enumerations with no enumerators
+-----------------------------------------
+
+Clang provides support for Microsoft extensions to support empty enums.
----------------
AaronBallman wrote:

```suggestion
Clang provides support for Microsoft extensions to support enumerations with no enumerators.
```

https://github.com/llvm/llvm-project/pull/159981