`proc type` doesn't match generic constraints `proc`

```nim
template foo*[T: proc](x: typedesc[T]): T = T(nil)

var m = foo(proc (s: int))
```

```
(proctype . . . . . . . . .)
(proctype . . . .
 (params
  (param :s.1 . .
   (i -1) .)) . . . .)
```

It is required to implement `default` for proc types and https://github.com/nim-lang/nimony/pull/1536 (because `std/streams` use massive proc pointers)
