* stack.c (frame_info): Use frame_register_unwind instead of

* stack.c (frame_info): Use frame_register_unwind instead of
saved_regs.  Mention when the SP is on the stack or in a register.
* frame.h (frame_register_unwind_ftype): Define.  Document.
(struct frame_info): Add field register_unwind and
register_unwind_cache.
(frame_register_unwind): Declare.
(generic_unwind_get_saved_register): Declare.
* frame.c (frame_register_unwind): New function.
(generic_unwind_get_saved_register): New function.
* blockframe.c (generic_call_dummy_register_unwind): New function.
(frame_saved_regs_register_unwind): New function.
(set_unwind_by_pc): New function.
(create_new_frame): New function.
(get_prev_frame): New function.