SI-7110 Warn about naked try without catch/finally

Before, this was allowed:

    scala> try ( 1 / 0 )
    java.lang.ArithmeticException: / by zero

But since the advent of util.Try, the subtle difference to the
following seems dangerous:

    scala> import util.Try
    import util.Try

    scala> Try ( 1 / 0 )
    res4: scala.util.Try[Int] = Failure(java.lang.ArithmeticException: / by zero)

Discussion: https://groups.google.com/d/topic/scala-language/fy2vXD_3fF8/discussion

Review by @JamesIry