godoc: fix lib/godoc/package.txt template
godoc: fix lib/godoc/package.txt template

- show documentation in text mode; e.g.:
http://localhost:7777/cmd/godoc/?f=text

- simplify template by using $ variable

R=r, adg
CC=golang-dev
http://codereview.appspot.com/4873045

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