Allow a function named 'get' to be generic (fixes #29746).

tests/language/regress_29349_test.dart

+// Copyright (c) 2017, 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.
+//
+// VMOptions=--generic-method-syntax
+
+List<T> get<T>(T item) => <T>[item];
+List<T> get2<T>(T item) => <T>[item];
+
+void main() {
+ print(get(1));
+ print(get2(1));
+}