Backend function used by resizeterm(), performing most of the work.
nlines
Height.
ncols
Width.
When resizing the windows, resize_term() blank-fills the areas that are
extended. The calling application should fill in these areas with
appropriate data. The resize_term() function attempts to resize all
windows. However, due to the calling convention of pads, it is not
possible to resize these without additional interaction with the
application.