The function `mouse-drag-and-drop-region' couldn't cut/move the
selected region when `mark-even-if-inactive' is t.

Say execute `emacs -Q` then evaluate
    (custom-set-variables
     '(mark-even-if-inactive nil)
     '(mouse-drag-and-drop-region t))
When I use mouse to drag and drop a selected region, the region is not
cut and pasted; it is copied and pasted instead.

The attached patch binds `mark-even-if-inactive' to t within the body
of `mouse-drag-and-drop-region'.

--
shynur