(read_minibuf_unwind): Call resize_mini_window with

(read_minibuf_unwind): Call resize_mini_window with
new parameter.
(read_minibuf): Use prompt_end_charpos instead
of minibuffer_prompt_length.
(read_minibuf_unwind): Ditto.
(Fminibuffer_complete_and_exit): Ditto.
(Fminibuffer_complete_word): Ditto.
(Fminibuffer_prompt_end): Ditto.
(read_minibuf): Return mini-buffer contents
without the prompt.
(read_minibuf): Set minibuf_prompt_width to the
current column after inserting prompt.
(Fminibuffer_prompt_width): Return minibuf_prompt_width.