This enable the following flexible macro signature when there is
no BOOST_PP_VARIADICS support:
BOOST_FUSION_ADAPT_STRUCT(
struct_name,
(member_type0, member_name0)
(BOOST_FUSION_ADAPT_AUTO, member_name1)
(,member_name2)
...
)
If BOOST_PP_VARIADICS is active then there is quite more flexibility as it
allows to avoid the type specification:
BOOST_FUSION_ADAPT_STRUCT(
struct_name,
(member_type0, member_name0)
(BOOST_FUSION_ADAPT_AUTO, member_name1)
(,member_name2)
(member_name3)
...
)