Allow lexically declared "arguments" in function scope in sloppy mode.

test/mjsunit/regress/regress-4577.js

Index: test/mjsunit/regress/regress-4577.js
diff --git a/test/mjsunit/bugs/bug-4577.js b/test/mjsunit/regress/regress-4577.js
similarity index 79%
rename from test/mjsunit/bugs/bug-4577.js
rename to test/mjsunit/regress/regress-4577.js
index de2f843965de8f0da6244334e722194a4353008f..98557744d626985049ece7bcd49e3fab65299b2d 100644
--- a/test/mjsunit/bugs/bug-4577.js
+++ b/test/mjsunit/regress/regress-4577.js
@@ -11,3 +11,9 @@ function g({arguments}) {
   return arguments === 42;
 }
 assertTrue(g({arguments: 42}));
+
+function foo() {
+  let arguments = 2;
+  return arguments;
+}
+assertTrue(foo() === 2);

[adamk, 2016/08/30 20:45:57]

assertEquals(2, foo());

[lpy, 2016/09/01 01:17:30]

Done.