patch 9.0.0206: redraw flags are not named specifically

Problem:    Redraw flags are not named specifically.
Solution:   Prefix "UPD_" to the flags, for UPDate_screen().
diff --git a/src/gui_haiku.cc b/src/gui_haiku.cc
index 1dd29b7..78a444a 100644
--- a/src/gui_haiku.cc
+++ b/src/gui_haiku.cc
@@ -656,7 +656,7 @@
     // TODO here we could handle going to a specific position in the dropped
     // file (see src/gui_mac.c, deleted in 8.2.1422)
     // Update the screen display
-    update_screen(NOT_VALID);
+    update_screen(UPD_NOT_VALID);
 }
 
     // Really handle dropped files and folders.