Type parameter constraints on local functions

[Simn]

I don't think this is super duper useful, but I also don't see a reason for not allowing this just for the sake of consistency:

class Main {
	static public function main() {
		function f<T:String>(t:T) {}

		f("foo");
		f(12);
	}
}

[Simn]

This is supported now, but we still need tests.