bug#3142: 23.0.92; split-window-prefered-function should be able to use split-window-horizontally/split-window-vertically

[Stefan Monnier]

> Remains the question whether `split-window-preferred-function' should
> always operate on the selected window or have a window argument.  AFAICT
> nothing speaks for the window argument but the fact that people may have
> customized this already.  Omitting the window argument would allow users
> to put `split-window-vertically' directly as value of
> `split-window-preferred-function' without having to delve any deeper.

I agree it would make sense to operate on the selected-window rather
than pass an explicit window argument.


        Stefan