Add macros to define comparison operators to compare by reference or pointer interchangeably

Add macros to define comparison operators to compare by reference or pointer
interchangeably. This avoids redefining them in Node, Frame and RenderObject.
There are 2 macros, one for refcounted types and another of non-refcounted
ones.

R=eseidel@chromium.org, adamk@chromium.org

Review URL: https://codereview.chromium.org/309083003

git-svn-id: svn://svn.chromium.org/blink/trunk@175399 bbb929c8-8fbe-4397-9dbb-9b2b20218538