Clang enforces that a union's constexpr CTOR must initialize
one of the members. The spec is seemingly silent as to what
the rule on this is, however, making this non-constexpr results in clang
accepting the constructor.
Signed-off-by: Erich Keane <erich.keane@verizon.net>
Message-Id: <1454604300-1673-1-git-send-email-erich.keane@verizon.net>