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/debugger.c b/src/debugger.c
index 38d1fb6..e2f73cc 100644
--- a/src/debugger.c
+++ b/src/debugger.c
@@ -285,7 +285,7 @@
 
     --RedrawingDisabled;
     --no_wait_return;
-    redraw_all_later(NOT_VALID);
+    redraw_all_later(UPD_NOT_VALID);
     need_wait_return = FALSE;
     msg_scroll = save_msg_scroll;
     lines_left = Rows - 1;