gdb/

	gdb/
	* frame.c (frame_unwind_pc): Rename to ...
	(frame_unwind_pc_if_available): ... this.  New `pc' output
	parameter.  Change return type to int.  Gracefully handle
	gdbarch_unwind_pc throwing NOT_AVAILABLE_ERROR.  Return 0 if that
	happened, or 1 otherwise.
	(frame_unwind_pc): Reimplement on top of
	frame_unwind_pc_if_available.
	(get_frame_func): Rename to ...
	(get_frame_func_if_available): New `pc' output parameter.  Change
	return type to int.  Gracefully handle the PC not being available.
	(get_frame_func): Reimplement on top of
	get_frame_func_if_available.
	(select_frame): Handle the PC being unavailable.
	(get_prev_frame): Handle the PC being unavailable.
	(get_frame_pc_if_available): New.
	(get_frame_address_in_block_if_available): New.
	(find_frame_sal): Handle the frame PC not being available.
	* frame.h (get_frame_pc_if_available): Declare.
	(get_frame_address_in_block_if_available): Declare.
	(get_frame_func_if_available): Declare.
	* stack.c (print_frame_info): Handle the PC being unavailable.
	(find_frame_funname): Ditto.
	(print_frame): Handle the PC being unavailable.
	(get_frame_language): Ditto.
	* blockframe.c (get_frame_block): Ditto.
	* macroscope.c (default_macro_scope): Ditto.
	* tui/tui-stack.c (tui_show_frame_info): Ditto.