[clang] [clang-repl] Allow private type aliases in out-of-line member function return types (PR #178842)

[Vassil Vassilev via cfe-commits]

https://github.com/vgvassilev approved this pull request.

Lgtm! Can you squash everything in one commit and write a descriptive commit message. Please include the issue we fix so that it can be closed automatically. 

https://github.com/llvm/llvm-project/pull/178842