Cgraph thunk reorg

[Mike Stump]

On May 6, 2011, at 5:12 AM, Jan Hubicka wrote:
>  2) As real functions calling the function they are associated with.
> 
>      Because backend don't handle alternative entry points, we really implement
>      thunks as small functions that usually tail call into the associated
>      functions after doing adjustments to THIS.

I don't like the word usually here...  that tail call for non-adjusting covariant returns and non-covariant returns, and a normal call otherwise.... Since this is just the email description, not a problem, but I did want to ensure people don't think of thunks as tail calling.