Make sure that presence of `@autoclosure` attribute handled
in one place - `matchCallArguments`, which makes it possible
to remove the rest of (now redundant) autoclosure related
logic scattered throughout solver.
Increase solution score when performing function conversions where only
one side has `@autoclosure`. That is going to help pick the best overload
when only difference lays in presence of such attribute.
e.g.
```swift
func foo(_: @autoclosure () -> Int) {}
func foo(_: () -> Int) {}
```
If the argument is itself `@autoclosure` it's preferable to use overload
with `@autoclosure` attribute, otherwise `() -> Int` should be used.
Resolves: rdar://problem/37160679