demos: add some fflushes for windows
diff --git a/progs/demos/streaming_rect.c b/progs/demos/streaming_rect.c
index 294f9c3..f65ac4c 100644
--- a/progs/demos/streaming_rect.c
+++ b/progs/demos/streaming_rect.c
@@ -153,6 +153,7 @@
 
       GLfloat fps = Frames / seconds;
       printf("%d frames in %6.3f seconds = %6.3f FPS\n", Frames, seconds, fps);
+      fflush(stdout);
 
       drift_increment = 2.2 * seconds / Frames;
       T0 = t;