gdb/
Code cleanup.
* frame-unwind.c (frame_unwind_find_by_frame): Remove the return type
and returned value. New comment from frame-unwind.h.
* frame-unwind.h (frame_unwind_find_by_frame): Remove the return type.
Extend the comment.
* frame.c (get_frame_id, frame_unwind_register_value)
(create_new_frame, get_prev_frame_1, frame_unwinder_is)
(get_frame_type, frame_unwind_arch): Do not use the return value of
frame_unwind_find_by_frame.