Add noexcept to shared_ptr owner comparisons (LWG 2873)
* include/bits/shared_ptr_base.h (__shared_ptr::owner_before)
(__weak_ptr::owner_before, _Sp_owner_less::operator()): Add noexcept
specifiers as per LWG 2873 and LWG 2942.
* testsuite/20_util/owner_less/noexcept.cc: New.
* testsuite/20_util/shared_ptr/observers/owner_before.cc: Test
noexcept guarantees.
* testsuite/20_util/weak_ptr/observers/owner_before.cc: Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@248874 138bc75d-0d04-0410-961f-82ee72b054a4