[libcxx] Make std::tuple<> trivially constructible

Summary:
This is not mandated by the Standard, but it's nonetheless a nice
property to have, especially since it's so easy to implement. It
also shrinks our bug list!

PR41714

Reviewers: mclow.lists, EricWF

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D62618

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@363075 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed