Correct "is Function" porting

[andrew-git]

as3 code for example:

package {
    public class Issue {
        public function Issue() {
            if(f is Function){}
        }
    }
}

expected result

class Issue
{
    public function new()
    {
        if(Reflect.isFunction(f)){}
    }
}

actual result

class Issue
{
    public function new()
    {
        if(Std.is(f, Function)){}
    }
}