With "set print vtbl on", I think ptype should also show
the vtable.

struct q {
  virtual ~q () = default;
  int x = 23;
};

q qqq;


(gdb) set print vtbl on
(gdb) ptype q
type = struct q {
  public:
    int x;

    ~q();
}


It would also be nice to have a ptype flag to enable this
per-use.

Finally, perhaps ptype/o should always show the vtables, since
the point of this is to understand the layout of the object in
memory.