patch 8.0.0631: can't build with Perl 5.26

Problem:    Perl 5.26 also needs S_TOPMARK and S_POPMARK defined.
Solution:   Define the functions when needed. (Jesin, closes #1748)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    631,
 /**/
     630,
 /**/