Allow parameter patterns, generalization of parameter types

[ilyash-b]

Related: #78

Now:

		F on_event(chc:ChannelHandlerContext, ev:ChannelEvent) {
			guard ev == ChannelEvent::active
			log("active")
		}

Should be:

		F on_event(chc:ChannelHandlerContext, ev:ChannelEvent::active) {
			log("active")
		}

Note that ChannelEvent::active is an instance, not a type