patch 8.1.0288: quickfix code uses cmdidx too often

Problem:    Quickfix code uses cmdidx too often.
Solution:   Add is_loclist_cmd(). (Yegappan Lakshmanan)

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    288,
 /**/
     287,
 /**/