Implement wheel movement during DND on Haiku

Implement wheel movement during DND on Haiku

* lisp/term/haiku-win.el (haiku-dnd-wheel-count): New defvar.
(haiku-note-wheel-click, haiku-handle-drag-wheel): New
functions.

* src/haiku_support.cc (EmacsWindow): Get rid of window ID
logic.
(MessageReceived, MouseMoved, be_drag_message): Use thread ID to
identify windows instead of window ID.

* src/haikuselect.c (Fhaiku_drag_message): Record whether or not
the DND frame is a valid drop target.
(haiku_note_drag_wheel): New function.
(syms_of_haikuselect): New defvar.

* src/haikuterm.c (haiku_read_socket): Call
`haiku_note_drag_wheel' when appropriate.
* src/haikuterm.h: Update prototypes.