patch 8.0.0535: memory leak when exiting from within a user function

Problem:    Memory leak when exiting from within a user function.
Solution:   Clear the function call stack on exit.

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    535,
 /**/
     534,
 /**/