UCSD-PL/RefScript — pull request #26 by panagosg7 (2014-09-16 10:43:30+00:00)
Title: Varinit

Allowing a phi variables to be uninitialized when joining environments.

In case of an uninitialized loop phi variable, e.g.
```
var i;
var sum = 0;
while (n > 0) {
i = n;
sum += i;
}
return sum;
```
The "invariant" `T_i` type for `i` will be: `number + undefined`.

Types need to be aligned (`ziptype`) when subtyping the "base" type (before loop) and "step" type (after loop body) against `T_i`.