Loosen Constructor super()/this() call restrictions

[Howard Lovatt]

A few notes:

1. It is useful to be able to initialise fields before super is
called, so that super can call instance methods defined in the derived
class. This is what inner class do for their outer pointer.

2. You will need definite assignment, could be as simple as no super
call inside a block (if, for, etc.) and only one call to super

3. You shouldn't be able to access super fields or any instance
methods before super.

  -- Howard.