patch 8.1.0844: when timer fails test will hang forever

Problem:    When timer fails test will hang forever.
Solution:   Use reltime() to limit waiting time. (Ozaki Kiichi, closes #3878)

src/version.c

@@ -783,6 +783,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    844,
 /**/
     843,
 /**/