bug#11795: 24.1.50; wdired: C-c C-c loses marks and positions of renamed files

[Juri Linkov]

> My suggestion would be to just delete the according lines so that they
> cannot cause trouble, simply with `delete-region'.  That should not do
> any harm.

I'm afraid `delete-region' will do harm especially at this stage closer
to the release because it needs heavy testing for possible failures.

Wdired worked correctly for a long time without `dired-add-file', so
it's better to avoid using `dired-add-file' and low-level `delete-region'.

`revert-buffer' already does its work well and propagates name changes
to other dired buffers where these files may also be shown.

The original request was about keeping markers of renamed files,
so what is needed is to use just `dired-remember-marks' and
`dired-mark-remembered' (and also another pair of functions
`dired-save-positions' and `dired-restore-positions').

There is no problem of getting the right names from places where
changes were made.  This should be implemented in the same place
in `wdired-do-renames' that currently has information about old and new
file names and their markers.  The same place in `wdired-do-renames'
can modify the remembered list of markers accordingly.
IOW, keep the same logic in `wdired-do-renames' as it has now,
but modify the `wdired-old-marks' variable instead of operating
on the dired buffer.