patch 8.1.0897: can modify a:000 when using a reference

Problem:    Can modify a:000 when using a reference.
Solution:   Make check for locked variable stricter. (Ozaki Kiichi,
            closes #3930)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 4c03470..6982ddf 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -1248,7 +1248,7 @@
     if (argvars[0].v_type == VAR_LIST)
     {
 	if ((l = argvars[0].vval.v_list) != NULL
-		&& !tv_check_lock(l->lv_lock,
+		&& !var_check_lock(l->lv_lock,
 					 (char_u *)N_("add() argument"), TRUE)
 		&& list_append_tv(l, &argvars[1]) == OK)
 	    copy_tv(&argvars[0], rettv);
@@ -1256,7 +1256,7 @@
     else if (argvars[0].v_type == VAR_BLOB)
     {
 	if ((b = argvars[0].vval.v_blob) != NULL
-		&& !tv_check_lock(b->bv_lock,
+		&& !var_check_lock(b->bv_lock,
 					 (char_u *)N_("add() argument"), TRUE))
 	{
 	    int		error = FALSE;
@@ -3579,7 +3579,7 @@
 
 	l1 = argvars[0].vval.v_list;
 	l2 = argvars[1].vval.v_list;
-	if (l1 != NULL && !tv_check_lock(l1->lv_lock, arg_errmsg, TRUE)
+	if (l1 != NULL && !var_check_lock(l1->lv_lock, arg_errmsg, TRUE)
 		&& l2 != NULL)
 	{
 	    if (argvars[2].v_type != VAR_UNKNOWN)
@@ -3615,7 +3615,7 @@
 
 	d1 = argvars[0].vval.v_dict;
 	d2 = argvars[1].vval.v_dict;
-	if (d1 != NULL && !tv_check_lock(d1->dv_lock, arg_errmsg, TRUE)
+	if (d1 != NULL && !var_check_lock(d1->dv_lock, arg_errmsg, TRUE)
 		&& d2 != NULL)
 	{
 	    /* Check the third argument. */
@@ -7266,8 +7266,9 @@
     }
     else if (argvars[0].v_type != VAR_LIST)
 	semsg(_(e_listblobarg), "insert()");
-    else if ((l = argvars[0].vval.v_list) != NULL && !tv_check_lock(l->lv_lock,
-				      (char_u *)N_("insert() argument"), TRUE))
+    else if ((l = argvars[0].vval.v_list) != NULL
+	    && !var_check_lock(l->lv_lock,
+				     (char_u *)N_("insert() argument"), TRUE))
     {
 	if (argvars[2].v_type != VAR_UNKNOWN)
 	    before = (long)tv_get_number_chk(&argvars[2], &error);
@@ -9698,7 +9699,7 @@
 	if (argvars[2].v_type != VAR_UNKNOWN)
 	    semsg(_(e_toomanyarg), "remove()");
 	else if ((d = argvars[0].vval.v_dict) != NULL
-		&& !tv_check_lock(d->dv_lock, arg_errmsg, TRUE))
+		&& !var_check_lock(d->dv_lock, arg_errmsg, TRUE))
 	{
 	    key = tv_get_string_chk(&argvars[1]);
 	    if (key != NULL)
@@ -9781,7 +9782,7 @@
     else if (argvars[0].v_type != VAR_LIST)
 	semsg(_(e_listdictblobarg), "remove()");
     else if ((l = argvars[0].vval.v_list) != NULL
-			       && !tv_check_lock(l->lv_lock, arg_errmsg, TRUE))
+			      && !var_check_lock(l->lv_lock, arg_errmsg, TRUE))
     {
 	idx = (long)tv_get_number_chk(&argvars[1], &error);
 	if (error)
@@ -10128,7 +10129,7 @@
     if (argvars[0].v_type != VAR_LIST)
 	semsg(_(e_listblobarg), "reverse()");
     else if ((l = argvars[0].vval.v_list) != NULL
-	    && !tv_check_lock(l->lv_lock,
+	    && !var_check_lock(l->lv_lock,
 				    (char_u *)N_("reverse() argument"), TRUE))
     {
 	li = l->lv_last;
@@ -12112,7 +12113,7 @@
     else
     {
 	l = argvars[0].vval.v_list;
-	if (l == NULL || tv_check_lock(l->lv_lock,
+	if (l == NULL || var_check_lock(l->lv_lock,
 	     (char_u *)(sort ? N_("sort() argument") : N_("uniq() argument")),
 									TRUE))
 	    goto theend;