Flashy scrolling flushes typeout when it shouldn't

[Tim McNerney <TIM at MIT-OZ>]

In ZWEI in Release 5.0 [GC'd Beta Test rev 3], dusty plum, on Lisp Machine Apiary-5 (3600):

It is entirely reasonable to flush typeout when one scrolls the window with the mouse in
one window mode (default).  However, in two window mode when one scrolls the window that
the typeout window is NOT obscuring (intentionally, or by accidentally bumping the mouse
into the flashy scrolling region), the typeout window really shouldn't be flushed.