[llvm] [MSVC][Demangling] Make Microsoft demangling more configurable (PR #202702)

[Fred Tingaud via llvm-commits]

frederic-tingaud-sonarsource wrote:

This PR is a merge of four related commits on my side, which I merged together because I think that is the preferred format. I'd be happy to change it to a stack of tiny commits if that makes the review easier.

https://github.com/llvm/llvm-project/pull/202702