Forward-ported staplog.c crash support (PR 10644).

Forward-ported staplog.c crash support (PR 10644).
* staplog.c (get_rchan): Separated original relayfs code and current
  relayfs code.
  (get_rchan_buf): Ditto.
  (output_cpu_logs): Ditto.
  (get_rchan_addr): Handles original relayfs code detection.
  (setup_global_data): Looks for '_stp_relay_data' structure instead of
  '_stp_utt' structure.
  (open_output_file): Improved error message.
* runtime/transport/relay_v2.c: Rearranged struct _stp_relay_data_type to
  make things a bit easier for staplog.c.
* runtime/transport/relayfs.c: Ditto