Dispatch issue with parametric methods where subtype constraint is a Type

Consider (on 0.4):

``` julia
julia> f{T<:Type{Int}}(::T) = true;

julia> f(Float64)
true
```

I think this should be a MethodError. It seems like `f` is applicable for any DataType, not just `Type{Int}`.

On 0.3, `f(Float64)` is in fact a MethodError, but so is `f(Int)`, which I would expect to work, so while the behavior has changed it doesn't seem like this is a regression.
