safer casts - take II

[Janice Caron]

The case for dynamic cast is closed. I just heard from the powers that
be that std.conv.to will support an exception-throwing dynamic cast in
the next Phobos. So it's

    dst = cast(T)src;  // non-throwing dynamic cast
    dst = to!(T)(src);  // throwing dynamic cast

Hopefully everyone's happy now.

Does anyone have a problem with the proposal /apart/ from dynamic cast failure?