patch 8.2.2897: Vim9: can use reserved words at the script level

Problem:    Vim9: can use reserved words at the script level.
Solution:   Check variable names for reserved words. (closes #8253)
diff --git a/src/eval.c b/src/eval.c
index 008b032..8e55435 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1309,6 +1309,9 @@
     {
 	cc = *endp;
 	*endp = NUL;
+	if (in_vim9script() && check_reserved_name(lp->ll_name) == FAIL)
+	    return;
+
 	if (lp->ll_blob != NULL)
 	{
 	    int	    error = FALSE, val;