Implement LWG2733: [fund.ts.v2] gcd / lcm and bool.  We already did tbis for C++17, so replicate the changes in experimental.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@292962 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed