- Explicitly save the stat()'s errno so that we can be sure we're

- Explicitly save the stat()'s errno so that we can be sure we're
  testing the right thing lower down (and so that future code doesn't
  always have to remember to save it off and restore it).
- Improved a chunk of link_dest code.
- Handle the removal of a non-regular file without so much duplicated
  code.