Interface Changes

- June 12, 2009: vector0 is now vector0<> as per Boost Trac Ticket #1608
  to follow MPL more closely.
- September 24, 2009: added nview and friends
- October 12, 2009: the accumulator is the first argument to the functor of
  fold and accumulate. Fixes Boost Trac Ticket #2355.
- October 30, 2009: Added support for associative iterators & views.
  Renamed associative_sequence_tag to associative_tag. Fixes Boost Trac
  Ticket #3473.
- April 4, 2010: Added array support, BOOST_FUSION_ADAPT_TPL_STRUCT,
  BOOST_FUSION_ADAPT_ASSOC_TPL_STRUCT, BOOST_FUSION_ADAPT_ASSOC_STRUCT_NAMED and
  BOOST_FUSION_ADAPT_ASSOC_STRUCT_NAMED_NS
- April 5, 2010: Added BOOST_FUSION_DEFINE_STRUCT,
  BOOST_FUSION_DEFINE_TPL_STRUCT, BOOST_FUSION_DEFINE_ASSOC_STRUCT and
  BOOST_FUSION_DEFINE_ASSOC_TPL_STRUCT
- June 18, 2010: Added reverse_fold, iter_fold and reverse_iter_fold. Fixes
  Boost Trac Ticket #1623.