Handle super != and ?

Fix two bugs regarding != and argument definition test.

issue 2554
issue 6050
Review URL: https://codereview.chromium.org//11225006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@13837 260f80e4-7a28-3924-810f-c04153c831b5
3 files changed