[PATCH] Fix overflow in __gnu_cxx::__numeric_traits::__min

[Jonathan Wakely]

On 01/12/17 14:02 +0000, Jonathan Wakely wrote:
>Is there a reason we left-shift into the sign bit, causing undefined
>behaviour? The approach used in std::numeric_limits seems better.

The current code warns with -Wpedantic -Wsystem-headers:

/usr/include/c++/7/ext/numeric_traits.h:58:35: warning: overflow in implicit constant conversion [-Woverflow]
       static const _Value __min = __glibcxx_min(_Value);
                                   ^~~~~~~~~~~~~