[builtins] Unify the various versions of [[Call]] with a Call builtin.

test/mjsunit/harmony/proxies-function.js

Index: test/mjsunit/harmony/proxies-function.js
diff --git a/test/mjsunit/harmony/proxies-function.js b/test/mjsunit/harmony/proxies-function.js
index c024cef948f68a8dfc5f30ea8b0afe49aebcfd17..23b885a43eef5d8eb57bb6da5004949b8aafc002 100644
--- a/test/mjsunit/harmony/proxies-function.js
+++ b/test/mjsunit/harmony/proxies-function.js
@@ -120,9 +120,6 @@ function TestCall(isStrict, callTrap) {
   receiver = 333
   assertEquals(42, %_CallFunction(o, 11, 31, f))
   assertSame(o, receiver)
-  receiver = 333
-  assertEquals(42, %_CallFunction(null, 11, 31, f))
-  assertSame(isStrict ? null : global_object, receiver)
 
   var ff = Function.prototype.bind.call(f, o, 12)
   assertTrue(ff.length <= 1)  // TODO(rossberg): Not spec'ed yet, be lax.