go/printer, gofmt: smarter handling of multi-line raw strings

go/printer, gofmt: smarter handling of multi-line raw strings

If a multi-line raw string is the first token on a line, it
should not be indented because the following lines (belonging
to the raw string) are not indented either.

Adjusted src of ebnf/ebnf_test.go manually as it now is formatted
as expected.

gofmt -w src misc

Fixes #1072.

R=r
CC=golang-dev
https://golang.org/cl/4119056