gcc warnings with -Wshadow compiler flag

[nigels-com]

Looking at safe_dump_to.hpp there is a recurring pattern there of doing:

        typedef boost::stacktrace::detail::native_frame_ptr_t native_frame_ptr_t;

Which is understandable, on the face of it, improving clarity.

On the other hand, our codebase is using -Wshadow compiler flag on Linux and it is complaining about this in boost::stacktrace eventhough it's arguably a false alarm.

But looking more closely, we're already in the boost::stacktrace::detail namespace, are these additional typedefs still necessary?

[apolukhin]

Many thanks for the report!