[clang] [libclang/python] Add typing annotations for the Cursor class (PR #138103)

[Vlad Serebrennikov via cfe-commits]

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@@ -77,6 +77,8 @@ Clang Frontend Potentially Breaking Changes
 
 Clang Python Bindings Potentially Breaking Changes
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+- Calling methods on null-cursors now leads to an exception.
+- ``Cursor.from_location`` now returns ``None`` instead of a null-cursor.
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Endilll wrote:

```suggestion
- ``Cursor.from_location`` now returns ``None`` instead of a null cursor. This eliminates the last known source of null cursors.
```

https://github.com/llvm/llvm-project/pull/138103