Also compare frame_id_is_next in frapy_richcompare

Also compare frame_id_is_next in frapy_richcompare

The last frame in a corrupt stack stores the frame_id of the next frame,
so these two frames currently compare as equal.

So if you have a backtrace where the oldest frame is corrupt, this happens:

(gdb) py
 >f = gdb.selected_frame()
 >while f.older():
 >  f = f.older()
 >print(f == f.newer())
 >end
True

With this change, that same example returns False.

gdb/ChangeLog:

2021-02-07  Hannes Domani  <ssbssa@yahoo.de>

	* python/py-frame.c (frapy_richcompare): Compare frame_id_is_next.