Emacs on Windows: How to save line breaks in Unix style in undecided buffers by default.

[hans bennekop]

In unsaved buffers that are not linked to a file the end-of-line style
is 'undecided'.
In this case Emacs saves line breaks in DOS style (crlf) on Windows.
How can I set it up to use Unix line breaks (lf) by default?

Calling (prefer-coding-system 'utf-8-unix) or setting "" in
file-coding-system-alist to 'undecided-unix works as a quick fix, but
also causes DOS style files to be opened as Unix style files, which is
rather annoying.

Thank you!
Hans