Merge branch 'ipv6-overflow-arith'

Hannes Frederic Sowa says:

====================
overflow-arith: begin to add support for overflow builtins functions

I add a new header, linux/overflow-arith.h, as the central place to add
overflow and wrap-around checking functions. The reason I am doing so
is that it can make use of compiler supported builtin functions which
can leverage hardware.

As I need this for a fix in the ipv6 stack, which is also included in
this series, I propose to add it sooner than later over Davem's net
tree. This is also the reason why I start slowly with only the one
function I need at this time.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>