Respect new DND options when dragging to ourselves on Haiku

Respect new DND options when dragging to ourselves on Haiku

* lisp/mouse.el (mouse-drag-and-drop-region): Allow dragging to
the current frame if we know `return-frame' doesn't work.
* lisp/term/haiku-win.el (haiku-dnd-drag-handler): New function.
* src/haiku_support.cc (MouseMoved): Don't send drag motion
events for the drag frame.
* src/haikuselect.c (haiku_note_drag_motion_1)
(haiku_note_drag_motion_2, haiku_note_drag_motion): New
functions.
(syms_of_haikuselect): New variable `haiku-drag-track-function'.
* src/haikuterm.c (haiku_read_socket): Note mouse motion in that
case.q
* src/haikuterm.h: Update prototypes.