Fix generated drag-and-drop mouse rectangles

Fix generated drag-and-drop mouse rectangles

* lisp/x-dnd.el (x-dnd-get-drop-width-height): Handle window
width and height correctly.  Remove unused parameter.
(x-dnd-after-move-frame): New function.
(move-frame-functions): Add new hook.
(x-dnd-compute-root-window-position): New function.
(x-dnd-get-drop-x-y): Use that instead of `left' and `top'
parameters, which include the title bar.
(x-dnd-handle-xdnd): Update accordingly.
* src/xfns.c (Fx_translate_coordinates): New function.
(syms_of_xfns): New defsym.