Delete ffi-buffer-make and ffi-window-make

[aadcg]

ffi-window-make is a trivial method. The renderer package must define a renderer-window, from which window inherits so it's obvious that (make-instance 'window...) is defined and it instantiates with the required renderer logic.

The same argument is valid for ffi-buffer-make. In this case, a closer look needs to be taken since it is called from resurrect-buffer which doesn't make any sense.