Fix bug and rewrite display-buffer-split-window(-1).
* window.el (display-buffer-split-window-1): Remove max-size
argument and corresponding code.
(display-buffer-split-window): Remove handling of max-height and
max-width specifiers. Restore the pre Emacs 24 behavior where a
single-window frame could be split ignoring the min-height
specifier (then split-height-threshold value). For the
horizontal splitting, side equalling nil case call
display-buffer-split-window-1 with side argument set to 'right
instead of 'below, fixing a bug spotted by Štěpán Němec.