bug#1501: Emacs 22 loses undo buffer

[Chong Yidong]

There is insufficient information to diagnose the problem you reported.
If possible, please provide the C header file that demonstrates this
problem.  Also, provide *exact* instructions for reproducing the
problem---we need the exact keystrokes you entered, not a vague
description like "deleted approximately 100 or so lines".

Thanks.