patch 8.1.1116: cannot enforce a Vim script style

Problem:    Cannot enforce a Vim script style.
Solution:   Add the :scriptversion command. (closes #3857)

src/structs.h

@@ -79,6 +79,7 @@ typedef struct {
     scid_T	sc_sid;		// script ID
     int		sc_seq;		// sourcing sequence number
     linenr_T	sc_lnum;	// line number
+    int		sc_version;	// :scriptversion
 } sctx_T;
 
 /*