go/internal/gccgoimporter: ignore unexported and imported names

go/internal/gccgoimporter: ignore unexported and imported names

    Due to inlining, we can now see unexported functions and variables,
    and functions and variables imported from different packages.
    Ignore them rather than reporting them from this package.

    Handle $hash and $equal functions consistently, so that we discard the
    inline body if there is one.

    Ignore names created for result parameters for inlining purposes.

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/180758

From-SVN: r272023