Silver: Allow @escaping in closure declaration that contain escaping closures as its parameters

In Silver @escaping is not allowed when declaring closures, however it often needs to be used on a parameter, when closure itself takes the escaping closure as a parameter.

//allowed in Swift
var closureWithEscapingClosureAsParameterº: ( (@escaping (String) -> Void) -> Void)?

Thanks, logged as bugs://76998

bugs://76998 got closed with status fixed.