Quick fix for parameter type based on use

[gavinking]

So, thanks to @thradec and #58, in the following code:

  void x<T>(T y)  {
        print(y);
  }

I get proposed the quickfix Add generic type constraint 'T satisfies Object'. But there's actually another potential fix,namely to change the parameter type to T&Object, giving us:

  void x<T>(T&Object y)  {
        print(y);
  }

The same quick fix is also very relevant for formal attributes, not just for parameters. For example:

  class X<T>()  {
        formal T y;
        print(y);
  }

[gavinking]

@thradec you want to take this one? I think it's very similar to the one you just did....

[gavinking]

Don't worry, I did this one.