Display BUFFER in a new window on SIDE of the selected frame.
SIDE must be one of `left', `top', `right' or `bottom'. SLOT
specifies the slot to use. ALIST is an association list of
symbols and values as passed to `display-buffer-in-side-window'.
This function may be called only if no window on SIDE exists yet.
The new window automatically becomes the "major" side window on
SIDE. Return the new window, nil if its creation window failed.