Before we had a function that updated display-buffer-alist whenever
the frame's size was changed, so that info windows like flymake or
flycheck open would snap to either the bottom or right hand side of the
frame depending on whether the window manager had the frame squeezed
vertically (like when you have two windows side by side split
vertically).
Now instead of having that function run every time the frame resizes,
we just make the 'side property a function that should get evaluated
each time the property is read. The function returns either 'bottom or
'right depending on the frame's current size in pixels.
John Turner