integral overflow and integral conversions

[Joseph S. Myers]

I am confident in the correctness of the tests I wrote for overflow for C 
(gcc.dg/overflow-warn-[1234].c).  This doesn't necessarily mean the 
present mixture of ways of indicating that an expression of integer 
constants is not an integer constant expression (for whatever combination 
of reasons involving overflow, division by zero, out-of-range shifts, 
etc.) is the best implementation approach.

-- 
Joseph S. Myers
joseph@codesourcery.com