[PATCH] Clarify that -fwrapv covers all signed arithmetic overflow

[Joseph Myers]

On Tue, 17 Nov 2015, Paolo Bonzini wrote:

> * it doesn't promise that GCC will never rely on undefined behavior
> rules for signed left shifts

I think we should remove the ", but this is subject to change" in 
implement-c.texi (while replacing it with noting that ubsan will still 
diagnose such cases, and they will also be diagnosed where constant 
expressions are required).

-- 
Joseph S. Myers
joseph@codesourcery.com