Back out r41001 for the moment ("Add log_user_text. Useful for log dumps, which are...

Back out r41001 for the moment ("Add log_user_text. Useful for log dumps, which are needed by rev_deleted")
If applied in one piece, it should probably fill in log_user_text... but that would be very slow in production environments.
If it has to be able to work with an online update in production, it should probably allow for a NULL log_user_text value rather than '', which is eery