OREGISTER is unused.

All remaining uses of Node.Reg use REGSP.

Change-Id: I51cf06826867e576baabd568e04f96d2634f5cad
Reviewed-on: https://go-review.googlesource.com/31856
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>