* frame.h (frame_unwind_arch): New.

	* frame.h (frame_unwind_arch): New.
	(frame_unwind_caller_arch): Likewise.
	* frame-unwind.h (frame_prev_arch_ftype): New type.
	(struct frame_unwind): New member prev_arch.
	* frame.c (struct frame_info): New member prev_arch.
	(frame_unwind_arch): New function.
	(frame_unwind_caller_arch): Likewise..
	(get_frame_arch): Reimplement in terms of frame_unwind_arch.
	* sentinel-frame.c (sentinel_frame_prev_arch): New function.
	(sentinel_frame_unwinder): Install it.

	* frame.c (frame_pc_unwind): Use frame_unwind_arch instead
	of get_frame_arch.
	(frame_unwind_register_value): Likewise.
	(frame_unwind_register_signed): Likewise.
	(frame_unwind_register_unsigned): Likewise.
	* frame-unwind.c (frame_unwind_got_optimized): Likewise.
	(frame_unwind_got_register): Likewise.
	(frame_unwind_got_constant): Likewise.
	(frame_unwind_got_bytes): Likewise.
	(frame_unwind_got_address): Likewise.

	* frame.h (enum frame_type): New value ARCH_FRAME.
	* frame.c (fprint_frame_type): Handle ARCH_FRAME.
	* stack.c (print_frame_info): Likewise.