Enable syntax-only support for generic functions by default.

tests/language/generic_methods_generic_function_parameter_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
-// DartOptions=--generic-method-syntax
 // VMOptions=--generic-method-syntax
 
 import "package:expect/expect.dart";
 
 class C<T> {
   bar<V>(T t, int u, V v) => t + u + v;
   foo<U>(bar<V>(T t, U u, V v)) => bar<int>(1, 2, 3);
 }
 
 main() {
   var c = new C<int>();
   Expect.equals(6, c.foo<int>(c.bar));
 }