[condense] Preserve altPath destinations for functions

This PR changes (fixes?) condenser behavior to preserve the altPath to the type of a def when its type is a function. Previously, the condenser would change the type to `?`.

For example, consider the code below.

```javascript
function a(){}
var b = a;
```

Without this PR, the condenser produces:

```
{
  "!name": "fn",
  "a": {
    "!span": "9[0:9]-10[0:10]",
    "!type": "fn()"
  },
  "b": "?"
}
```

With this PR, the condenser emits `{ ... "b": "a" ... }`, denoting that the altPath `b` refers to the type `b`.