(temp_output_buffer_show): Don't set prevent_redisplay_optimizations_p.

src/window.c

@@ -3145,7 +3145,9 @@ temp_output_buffer_show (buf)
   BEGV = BEG;
   ZV = Z;
   SET_PT (BEG);
+#if 0  /* rms: there should be no reason for this.  */
   XBUFFER (buf)->prevent_redisplay_optimizations_p = 1;
+#endif
   set_buffer_internal (old);
 
   if (!EQ (Vtemp_buffer_show_function, Qnil))