Null references redux

[BCS]

Hello Walter,

> Jeremie Pelletier wrote:
> 
>> It could even be used for any type, the default initializer in D is a
>> cute idea, but not a performance friendly one. I would much prefer
>> the compiler to allow "int a" but warn me if I use it before
>> assigning anything to it than assigning it to zero, and then
>> assigning it to the value I wanted. "= void" is nice but I'm pretty
>> sure I'm way over a thousand uses of it so far.
>> 
> The compiler, when -O is used, should remove nearly all the redundant
> initializations.
> 

Sweet, so you already have a bunch of the logic needed to check make sure 
non-null references get initialized.