[es8] Throw SyntaxError when tail call expressions occur in non-strict mode.

test/message/syntactic-tail-call-of-identifier.out

Index: test/message/syntactic-tail-call-of-identifier.out
diff --git a/test/message/syntactic-tail-call-of-identifier.out b/test/message/syntactic-tail-call-of-identifier.out
index 8ad7b4e9ed7cbfe608bd2801093be098be5a5dd4..393bbc657c925a9c6e950a091acf9fff2dacac51 100644
--- a/test/message/syntactic-tail-call-of-identifier.out
+++ b/test/message/syntactic-tail-call-of-identifier.out
@@ -1,4 +1,4 @@
-*%(basename)s:8: SyntaxError: Unexpected expression inside tail call
+*%(basename)s:9: SyntaxError: Unexpected expression inside tail call
   return continue   x  ;
                     ^
 SyntaxError: Unexpected expression inside tail call