Avoid implicit ambiguity after fix for SI-6667

   trait Statistics {

      import Stats._

      case class SpecsStatistics(fragments: Seq[ExecutedFragment] = ArrayBuffer()) {
        private implicit val statsMonoid = Stats.StatsMonoid

        // Two identifiers in scope of the implicitly searched type,
        // `statsMonoid` and `StatsMonoid` => ambiguity. Scala 2.10.0
        // and below would not report that ambigutity if the implicit
        // search was performed in a context with an expected type,
        // as the `silent` typer mode prevented the error being emitted.
        // Instead, it would proceed to search the implicit scope, which
        // in this case would unambiguously find `StatsMonoid`.
        //
        // Scala 2.10.1 uniformly reports the ambiguity of in-scope
        // implicits.
    }