Variable initialization
-----------------------

undefined
---------
The value of these variables is the undefined value. The exact behaviour
depends on the compiler options. There are three possibilities:
  * compile-time error (if possible to detect)
  * run-time error (unless disabled)
  * the variables get arbitrary values.
    
    int i;
    int#[4] i;
    int^ i;


initialized
-----------

These variables are initialized. In this case they are zero, so they will
be placed in the "zero-initialized data" section in the final executable
file (unless they are on the stack, then they are simply assigned their
value).

    int i = 0;
    int#[4] i = [0,0,0,0];
    int^ i = none;


default
-------

Initialization with default values:

    int i = _;
    int#[4] i = _;
    int^ i = _;

This works on all types that have the "defval()" function in their namespace:

    namespace int {
        () defval(int ^value) {
            value^ = 0;
        }
    }

    // What about array types, pointers, optional types, etc?