My patch of 2016-08-26 to avoid calling a trivial default constructor
introduced TARGET_EXPRs initialized with void_node to express trivial
initialization.  But when this shows up in a VEC_INIT_EXPR, we weren't
prepared to handle it.  Fixed by handling it explicitly in
cxx_eval_vec_init_1.

	* constexpr.c (cxx_eval_vec_init_1): Handle trivial initialization.

From-SVN: r264442