godoc: ignore directories that begin with '.'
godoc: ignore directories that begin with '.'

Fixes issue 2017.

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/4675047

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