Parsing @{...} blocks along with other elements

See https://github.com/playframework/playframework/issues/3807

A template like this:

``` scala
@(x: String)
@x @{x}
```

produces the wrong code:

``` scala
_display_(x{{x}})
```

causing compile errors.

`@x @x`, `@{x} @x`, and `@{x} @{x}` work fine.
