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/quickfix.c b/src/quickfix.c
index e9cbcb3..54ae07d 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -4352,7 +4352,7 @@
     curwin->w_cursor.coladd = 0;
     curwin->w_curswant = 0;
     update_topline();		// scroll to show the line
-    redraw_later(VALID);
+    redraw_later(UPD_VALID);
     curwin->w_redr_status = TRUE;	// update ruler
     curwin = old_curwin;
     curbuf = curwin->w_buffer;
@@ -4573,7 +4573,7 @@
 	// Only redraw when added lines are visible.  This avoids flickering
 	// when the added lines are not visible.
 	if ((win = qf_find_win(qi)) != NULL && old_line_count < win->w_botline)
-	    redraw_buf_later(buf, NOT_VALID);
+	    redraw_buf_later(buf, UPD_NOT_VALID);
     }
 }
 
@@ -4827,7 +4827,7 @@
 	--curbuf_lock;
 
 	// make sure it will be redrawn
-	redraw_curbuf_later(NOT_VALID);
+	redraw_curbuf_later(UPD_NOT_VALID);
     }
 
     // Restore KeyTyped, setting 'filetype' may reset it.
@@ -6468,7 +6468,7 @@
 #ifdef FEAT_FOLDING
 	foldUpdateAll(curwin);
 #else
-	redraw_later(NOT_VALID);
+	redraw_later(UPD_NOT_VALID);
 #endif
     }