alias to connect with superclass's constructor

[Andy Valencia]

Consider the following, totally contrived, code.  The compiler 
tells me:

tst39.d(21): Error: constructor `tst39.B.this(string s)` is not 
callable using argument types `()`
tst39.d(21):        constructor `tst39.B.this` hides base class 
function `tst39.A.this`
tst39.d(21):        add `alias this = tst39.A.this` to 
`tst39.B`'s body to merge the overload sets

But I haven't yet found a way to use this guidance to resolve the 
error.  I _can_ add this to B:

```d
     this() {
         super():
     }
```

But I'm curious if there's a working example of getting this 
effect with the compiler-recommended alias usage?  My searches 
here and on the Duck have come up empty.

```d
class A {
     int a;

     this() {
         this.a = 1;
     }
}
class B : A {
     string b;

     this(string s) {
         super();
         this.b = s;
     }
}
void
main() {
     import std.stdio : writeln;

     auto a = new A();
     auto b1 = new B();
     auto b2 = new B("Hi, Mom!");
     writeln(b1.a, " - ", b1.b);
     writeln(b2.a, " - ", b2.b);
}
```