Adding noexcept-specification on tuple constructors (LWG 2899)

Adding noexcept-specification on tuple constructors (LWG 2899)

2019-04-28 Nina Dinka Ranns <dinka.ranns@gmail.com>

* libstdc++-v3/include/std/tuple:
(tuple()): Add noexcept-specification.
(tuple(const _Elements&...)): Likewise
(tuple(_UElements&&...)): Likewise
(tuple(const tuple<_UElements...>&)): Likewise
(tuple(tuple<_UElements...>&&)): Likewise
(tuple(const _T1&, const _T2&)): Likewise
(tuple(_U1&&, _U2&&)): Likewise
(tuple(const tuple<_U1, _U2>&): Likewise
(tuple(tuple<_U1, _U2>&&): Likewise
(tuple(const pair<_U1, _U2>&): Likewise
(tuple(pair<_U1, _U2>&&): Likewise
* libstdc++-v3/testsuite/20_util/tuple/cons/noexcept_specs.cc: New

From-SVN: r270632