RFC: 40 bit integer support

[Joseph S. Myers]

One more general point:

There are further issues around what we might call "extended types that 
behave much like integer and floating-point types", especially for C++; 
see my comment in PR 43622, and the references therein.  How to fix these 
(again, while avoiding hardcoding references to such types in 
target-independent code) should also be considered separately.

-- 
Joseph S. Myers
joseph@codesourcery.com