We need superclass constructor call syntax

[iconmaster5326]

Inside constructors, we need to be able to call superclass constructors. This should use syntax similar to #11.

Proposed syntax:

class a {
    new(int x) {}
}

class b {
    new(string y) {}
}

class c : a,b {
    new() {
        new(42);
    }

    new(int z) {
        // note that we can have statements before super-constructor calls,
        // and said calls are optional, anyways.
        // We'll issue a warning if not all superclasses have their constructors called for certain.
        @super new(z);
        @super(class b) new(z.toString());
    }
}