[swift-evolution] Rewrite imported C function signatures

[Carlos Rodríguez Domínguez]

I’ve been rethinking the proposal and maybe a more suitable syntax should be:

#override(socket(_:,_:,_:)->Int32)
func socket(domain:SocketDomain, type:SocketType, protocol:SocketProtocol) -> socket_t? {
	//…
}

In this way it is clearer that the idea is to bring func overriding to global functions.