[libunwind] [libunwind][Haiku] Fix signal frame unwinding (PR #135367)

[Trung Nguyen via cfe-commits]

trungnt2910 wrote:

Submitted a new implementation that uses Haiku's recent [special handling](https://github.com/haiku/haiku/commit/1e1ad7efc96f94447815373be60fc1cc74962c65) of the `commpage` in `dladdr` to detect the signal handler function.

This removes the need for both private headers and re-declarations of private symbols.

https://github.com/llvm/llvm-project/pull/135367