go spec: clarify address operators.
go spec: clarify address operators.

Fixes issue 1445.

R=r, rsc, iant, ken2
CC=golang-dev
http://codereview.appspot.com/4109041

tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,ssrl/go,tv42/old-go,tv42/old-go,ssrl/go,apparentlymart/golang,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,ssrl/go,dsriram/golang,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,gnanderson/go,apparentlymart/golang,dsriram/golang,apparentlymart/golang,gnanderson/go,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,apparentlymart/golang,dsriram/golang,dsriram/golang,gnanderson/go,ssrl/go,pombredanne/go-deleteme,ssrl/go,gnanderson/go,apparentlymart/golang,tv42/old-go,ssrl/go,apparentlymart/golang,gnanderson/go,ssrl/go,dsriram/golang,tv42/old-go,pombredanne/go-deleteme