spec: receiver types in method expressions can be parenthesized
spec: receiver types in method expressions can be parenthesized

Fixes issue 4457.

R=rsc, iant, r, ken
CC=golang-dev
https://codereview.appspot.com/6862046

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