patch 8.1.2320: insufficient test coverage for quickfix

Problem:    Insufficient test coverage for quickfix.
Solution:   Add more tests.  Fix uncovered problem. (Yegappan Lakshmanan,
            closes #5238)
diff --git a/src/version.c b/src/version.c
index bbc74f3..e1ffa9e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2320,
+/**/
     2319,
 /**/
     2318,