* infrun.c (handle_command, signals_info), infcmd.c
(signal_command): Use it.
* infrun.c, infcmd.c: Update docstrings for these commands.
* target.h (enum target_signal), target.c (signals), target.c
(target_signal_from_host, target_signal_to_host): Add
TARGET_SIGNAL_REALTIME_* and TARGET_SIGNAL_PRIO for lynx.
* config/tm-lynx.h: Define signal numbers for realtime events.