bug#431: 23.0.60; `display-buffer' opens vertical instead of horizontal windows

[martin rudalics <rudalics@gmx.at>]

 >  1) Start Emacs with ./src/emacs -Q -g 80x24
 >  2) C-x 4 f ~/.emacs
 >  3) Observe that the frame is split vertically, i.e. the new buffer
 >     is displayed in a window *below* the scratch buffer.
 >
 > Now repeat this with 160x24 instead of 80x24.  The frame is now
 > split horizontally and the new buffer is in a window to the *right*
 > of the original window.  It's a bug because the size of the frame
 > should not affect the direction of the default split.
 >
 > I just bootstrapped from CVS and it still happens.
 >
 > Hope this clarifies things a bit,

Users can avoid horizontal splitting by setting `split-width-threshold'
to nil.  They also can avoid vertical splitting (but for single-window
frames) by setting `split-height-threshold' to nil.

We can set the default of `split-width-threshold' to nil to get the
behavior you consider correct.  IIRC some people wanted the default
split to be horizontal for very wide frames.  I have no preferences
here.

martin