patch 8.1.1116: cannot enforce a Vim script style

Problem:    Cannot enforce a Vim script style.
Solution:   Add the :scriptversion command. (closes #3857)
diff --git a/src/proto/ex_cmds2.pro b/src/proto/ex_cmds2.pro
index 01d20db..29bdf6a 100644
--- a/src/proto/ex_cmds2.pro
+++ b/src/proto/ex_cmds2.pro
@@ -98,6 +98,7 @@
 void script_line_exec(void);
 void script_line_end(void);
 void ex_scriptencoding(exarg_T *eap);
+void ex_scriptversion(exarg_T *eap);
 void ex_finish(exarg_T *eap);
 void do_finish(exarg_T *eap, int reanimate);
 int source_finished(char_u *(*fgetline)(int, void *, int), void *cookie);