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/evalvars.c b/src/evalvars.c
index 16dfd0d..0b51ce1 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -3827,7 +3827,7 @@
 		else if (STRCMP(varname, "hlsearch") == 0)
 		{
 		    no_hlsearch = !di->di_tv.vval.v_number;
-		    redraw_all_later(SOME_VALID);
+		    redraw_all_later(UPD_SOME_VALID);
 		}
 #endif
 		goto failed;