Libc++ provides static assertions to detect reference binding issues inside tuple. This patch adds tests for those diagnostics. It should be noted that these static assertions technically violate the standard since it allows these illegal bindings to occur. Also see https://llvm.org/bugs/show_bug.cgi?id=20855 git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276078 91177308-0d34-0410-b5e6-96231b3b80d8