Re: `split-window-preferred-horizontally'

[martin rudalics]

> And BTW, split-window-preferred-function's docstring is horribly
> defcustom-oriented. `Vertically', `Horizontally' and `Sensibly' are
> *not* the values the variable can have...

But the doc-string is also what people customizing this read.  I once
used to put the valid values like `t' in the doc-string, and
`vertically' plus `t' in parentheses in the tags of the customization
interface and people complained.  Hence, I don't know how to do this
right.  Please write a better solution than the current one.