Fix drag-and-drop treatment of reused tooltip frames

Fix drag-and-drop treatment of reused tooltip frames

* src/androidfns.c (Fx_show_tip): Set `tip_window' to that of
any reused tooltip frame.

* src/haikufns.c (unwind_create_frame): Return whether the frame
was destroyed, as on X.
(unwind_create_tip_frame, haiku_create_frame, Fx_show_tip):
Synchronize with X.
(do_unwind_create_frame): New function.
(tip_window): Remove unused variable.

* src/nsfns.m (tip_window, unwind_create_tip_frame): Remove
unused variable `tip_window'.

* src/pgtkfns.c (pgtk_create_tip_frame): Rename to
pgtk_create_tip_frame.
(Fx_show_tip): Adjust accordingly.  Set `tip_window' to that of
any reused tooltip frame.

* src/w32fns.c (Fx_show_tip):

* src/xfns.c (Fx_show_tip): Set `tip_window' to that of any
reused tooltip frame.

(cherry picked from commit a4a458ffa4aaeb988ff4b6e6087c44dfdaf40a0b)