Rewrite minibuffer window resizing code

Rewrite minibuffer window resizing code

* src/frame.c (resize_mini_frames): New variable.
* src/window.c (resize_mini_window_apply): New function.
(grow_mini_window, shrink_mini_window): Remove PIXELWISE
argument.  Call resize_mini_window_apply to apply changes.
(Fresize_mini_window_internal): Call resize_mini_window_apply
to apply changes.
(Qwindow__resize_mini_frame): New symbol.
* src/window.h (grow_mini_window, shrink_mini_window): Adjust
external declarations.
* src/xdisp.c (resize_mini_window): For minibuffer-only frames
call 'window--resize-mini-frame' if resize_mini_frames is
non-nil.  Offload parts of logic to grow_mini_window and
shrink_mini_window which are now called without the PIXELWISE
argument.
(Vresize_mini_windows): Mention 'resize-mini-frames' in
doc-string.
* lisp/cus-start.el (resize-mini-frames): Add customization
support.
* lisp/window.el (window--resize-mini-window): Simplify code.
(window--resize-mini-frame): New function.
* doc/lispref/minibuf.texi (Minibuffer Windows): Describe new
option 'resize-mini-frames'.
* etc/NEWS: Mention new option 'resize-mini-frames'.