patch 8.1.0959: sorting large numbers is not tested

Problem:    Sorting large numbers is not tested and does not work properly.
Solution:   Add test.  Fix comparing lines with and without a number.
            (Dominique Pelle, closes #4017)
diff --git a/src/version.c b/src/version.c
index b2d76b7..0d9acf4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    959,
+/**/
     958,
 /**/
     957,