[backport] SI-6567 Warning for Option(implicitView(foo))

commit 284bd754fa5dfc8bc626b0c5ebe85d872dd044cb
Author: Jason Zaugg <jzaugg@gmail.com>
Date:   Sat Nov 3 16:19:46 2012 +0100

    SI-6567 Warning for Option(implicitView(foo))

    I've seen the reported problem before in the wild. It seems
    worthy of a special warning, so long as we advocate Option.apply
    as an alternative to `if (x == null) Some(x) else None`.

    It is behind -Xlint at the moment, an option that could do with
    some promotion.
    (cherry picked from commit 0bcb9e9169146e3f589c6c9f65cc4a5523b78120)