These changes fix the following problems (in his words):
- When a direcrory was extended, it's size was not updated.
- Moving directories didn't work.
- I had removed brelse() call after an error from bread(), because I
thought bread() would already free them, but it doesn't, so I have
reinserted the brelse() calls.
- I have changed pcfs_setattr to silently ignore attempts to change
uid, gid or access time of a file. This allows 'cp -p' without errors.
