[Checkers] Nullness checker

[Adam Warski]

Hello,

> The distinction between those two syntaxes is explained in section  
> 2.5.1 of
> the Checker Framework manual:
>
> http://groups.csail.mit.edu/pag/jsr308/current/checkers-manual.html#polymorphism
>
> Can you take a look and suggest improvements to that section if it  
> is not
> clear?

I must have been tired and didn't notice it - sorry :). It's pretty  
clear and with the "style note" explains any doubts.
I guess when looking at the table of contents I didn't associate  
polymorphism with generics, and didn't look there.

Adam