* Update the `archive' bit any time the file's time stamp is updated.
* Don't set the `archive' bit automatically for directories, and don't
update the time stamp of directories automatically. (There are the DOS
semantics.)
* Use DE_TIMES() to change the time stamp in deupdat(). Remove the extra
time stamp argument, as it's superfluous, and we may want to make changes
without touching the time stamp.
* Allow denode updates iff DE_MODIFIED is set after DE_TIMES() is called.
This allows us to make changes that are totally independent of the time
stamp, and to avoid rewriting the entry if the time stamp was ignored (e.g.
for directories).
* Make time stamp changes in setattr() asynchronous.
7aeec96289