Implement visual bell on Haiku like on X

Implement visual bell on Haiku like on X

* src/haiku_draw_support.cc
(BView_FillRectangleForVisibleBell): Delete function.
(BView_InvertRect): New function.

* src/haiku_support.cc (class EmacsView): Delete field
`visible_bell_color' and visible bell related methods.
(EmacsView_do_visible_bell): Delete function.
* src/haiku_support.h: Update prototypes.

* src/haikuterm.c (haiku_flash): Implement using
`BView_InvertRect'.
(haiku_beep): Use `haiku_flash' instead.