[clang] [llvm] [llvm][clang] Move RewriterBuffer to ADT. (PR #99770)

[Artem Dergachev via llvm-commits]

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

Works for me! IIUC nobody touched this code in a while, and that's probably because it's basically perfect for everyone's existing purposes. So I think moving it to ADT is appropriate.

https://github.com/llvm/llvm-project/pull/99770