compiler: Handle newlines in general comments.

compiler: Handle newlines in general comments.

    On comments, the specification says
    (http://golang.org/ref/spec#Comments): General comments start with the
    character sequence /* and continue through the character sequence */.
    A general comment containing one or more newlines acts like a newline,
    otherwise it acts like a space.

    Fixes golang/go#11528.

    Reviewed-on: https://go-review.googlesource.com/13064

From-SVN: r226794