Added tree numbering data structure.
Changed dominator query in CSE.
Removed skip-for-too-big patch in CSE.
Passes all.bash.

Change-Id: I98d7c61b6015c81f5edab553615db17bc7a58d68
Reviewed-on: https://go-review.googlesource.com/14326Reviewed-by: Keith Randall <khr@golang.org>