Revert "Reapply r27640: "Emit compile-time error on duplicate parameter names in typedefs.""

This reverts commit r27693.

R=johnniwinther@google.com

Review URL: https://codereview.chromium.org//23531079

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@27696 260f80e4-7a28-3924-810f-c04153c831b5
4 files changed