This was not properly implemented in GCC versions before 5.1, and
we still have some ports using older GCC versions.
See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43453#c7 and commit
6ac3994e3e582ec6a304c2a566bb1b0c69d507d2.
This code is adapted from similar code in SerenityOS and allows the
LIST_INITIALIZER1 test to pass with c++11 compliant compiler when
targeting an old c++ std librray that does not have
std::initializer_list.