unwind: disable stack trace with multiple personalities

* unwind.c (unwind_cache_invalidate, unwind_print_stacktrace,
unwind_capture_stacktrace): Disable stack tracing of non-default
personality processes.
unwind: constify binary_filename and symbol_name functions arguments

* unwind.c (call_action_fn, print_call_cb, sprint_call_or_error,
queue_put, queue_put_call): Add const qualifier to binary_filename and
symbol_name arguments.