spec: struct tags must be identical for types to be identical
spec: struct tags must be identical for types to be identical

We didn't mention this explicitly during our discussions,
but I think it fits the "identical types are spelled identically"
rule that we used.

R=gri, iant, ken2, r, rsc1
CC=golang-dev
http://codereview.appspot.com/1698043

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go