spec: clarify that newlines are kept in raw string literals
spec: clarify that newlines are kept in raw string literals

Fixes issue 8007.

LGTM=r
R=gri, r
CC=golang-codereviews
https://codereview.appspot.com/91510044

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang