PR gdb/2343

	PR gdb/2343
	* corelow.c (core_open): Use gdbarch_target_signal_from_host to
	translate signal numeric value from the target to GDB's enum
	target_signal.
	* gdbarch.c, gdbarch.h: Regenerated.
	* gdbarch.sh: Added two new functions target_signal_from_host and
	target_signal_to_host.
	* target.h (default_target_signal_from_host,
	default_target_signal_to_host): New functions - declarations.
	* signals/signals.c (struct gdbarch): New declaration.
	(default_target_signal_to_host, default_target_signal_from_host): New
	functions.