Fixes the DEFINE_STRUCT* macros after addition of type deduction for ADAPT_STRUCT

Hi @djowel and @K-ballo,

As I told in pull-request #9 the BOOST_FUSION_DEFINE_STRUCT macros were broken by my changes. This small commit fixes this problem. This way all tests are passing now.

As the BOOST_FUSION_ADAPT_STRUCT_FILLER* macros were changed to handle type deduction, this breaks the usage that BOOST_FUSION_DEFINE_STRUCT makes from them.

That is because BOOST_FUSION_DEFINE_STRUCT expects a simple tuple per attribute, while we now provide a tuple containing the size of a nested tuple which either has or not the type provided ( _i.e._ ((2, (member_type0, member_name0))) ). But in the case of the DEFINE* macros it would be a non-sense to support this kind of API as a field being currently defined cannot be deduced. :)

Cheers