patch 8.0.0517: there is no way to remove quickfix lists

Problem:    There is no way to remove quickfix lists (for testing).
Solution:   Add the 'f' action to setqflist(). Add tests. (Yegappan
            Lakshmanan)
diff --git a/src/version.c b/src/version.c
index 74dc550..1afe3ab 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    517,
+/**/
     516,
 /**/
     515,