New preemptive redisplay.

etc/NEWS

@@ -774,6 +774,14 @@ elements are deleted from the history list.
 
 ** Redisplay changes:
 
++++
+*** Preemtive redisplay now adapts to current load and bandwidth.
+
+To avoid preemping redisplay on fast computers, networks, and displays,
+the arrival of new input is now performed at regular intervals during
+redisplay.  The new variable `redisplay-preemption-period' specifies
+the period; the default is to check for input every 0.1 seconds.
+
 +++
 *** The mode line position information now comes before the major mode.
 When the file is maintained under version control, that information