bug#12507: `bookmark-write-file': use `write-file', not `write-region', to get backups

[Juri Linkov]

> Is your `custom-file' an "internal configuration file"?  Do you back it up?

`custom-file' has the opposite problem: it creates backups forcefully
even when backups should not be created in VC-controlled directories.

There is a bug in `custom-save-all', it binds `print-length'
and `print-level' to nil (but not `print-circle' to t), and
calls `save-buffer' that ignores the VC status and creates backups.

I have no problems with backups for configuration files
like e.g. .recentf~ or .emacs.desktop~ when a VCS is not used,
but while implementing backups for bookmarks please take into account
that it should not create backups in VC-controlled directories.

I guess normal `save-buffer' or `write-file' should take care about this
by creating backups only in non-VC directories, or creating numbered
backups if there are already existing numbered backups.