[clang] [clang] Fix constant evaluation of member pointer access into sibling class. (PR #150829)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Not quite sure I get what is going on but:

1- we need a release note
2- I need a better description of what is happening here.  Your tests doesn't make it clear that it is only the `e1` and `e2` expressions that are changing the behavior?  Is that correct?  
3- Please put a comment that explains what is happening. `Consider member in a sibling` is not nearly good enough.  A standards quite in particular is preferred.


https://github.com/llvm/llvm-project/pull/150829