Support multi implicit parameter list

Implicit function type can be curried just fine:

```scala
object Test {
  trait T; trait Q
  val a: implicit T => implicit Q => Int = 1

  implicit val q: Q = new Q {}
  val i1: Int = a(new T{})
  implicit val t: T = new T {}
  val i2: Int =  a
}
```

It would be nice to be able to define `a` as a def!:

```scala
def a(implicit t: T)(implicit q: Q): Int = 1
```