Use XCAR and XCDR instead of XCONS.

Use XCAR and XCDR instead of XCONS.
(Vresize_mini_config, resize_mini_frame,
resize_mini_initial_height): Removed.
(syms_of_xdisp): Remove references to these variables.
(resize_mini_window): Don't save window configuration, freeze
window starts instead.  Enlarge window until displaying an empty
buffer, then shrink it.  Make the function externally visible.
(redisplay_window): Treat frozen window start like forced start,
but accept point outside of the window.