patch 8.1.0800: may use a lot of memory when a function refers itself

Problem:    May use a lot of memory when a function creates a cyclic
            reference.
Solution:   After saving a funccal many times, invoke the garbage collector.
            (closes #3835)

src/version.c

@@ -791,6 +791,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    800,
 /**/
     799,
 /**/