updated for version 7.3.603
Problem:    It is possible to add replace builtin functions by calling
            extend() on g:.
Solution:   Add a flag to a dict to indicate it is a scope.  Check for
            existing functions. (ZyX)
diff --git a/src/structs.h b/src/structs.h
index abcb704..36440c3 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1106,6 +1106,11 @@
 #define VAR_DICT    5	/* "v_dict" is used */
 #define VAR_FLOAT   6	/* "v_float" is used */
 
+/* Values for "dv_scope". */
+#define VAR_SCOPE     1	/* a:, v:, s:, etc. scope dictionaries */
+#define VAR_DEF_SCOPE 2	/* l:, g: scope dictionaries: here funcrefs are not
+			   allowed to mask existing functions */
+
 /* Values for "v_lock". */
 #define VAR_LOCKED  1	/* locked with lock(), can use unlock() */
 #define VAR_FIXED   2	/* locked forever */
@@ -1181,6 +1186,7 @@
     int		dv_copyID;	/* ID used by deepcopy() */
     dict_T	*dv_copydict;	/* copied dict used by deepcopy() */
     char	dv_lock;	/* zero, VAR_LOCKED, VAR_FIXED */
+    char	dv_scope;	/* zero, VAR_SCOPE, VAR_DEF_SCOPE */
     dict_T	*dv_used_next;	/* next dict in used dicts list */
     dict_T	*dv_used_prev;	/* previous dict in used dicts list */
 };