Little fix for GCC4.7 support.

Tested on Ubuntu quantal with gcc4.7 and boost 1.51

After a failure of my project's compilation on this platform (BOOST_PP_ITERATION_FLAGS gets evaluated to 0, thus generating an error for the bad syntax 0() ), I found out on http://dev.ryzom.com/issues/1462 that a patch existed and that it was not applied to the base repository, although it seems to be applied on the deb package.

The drawback being that macros such as LUABIND_TUPLE_PARAMS would not be available on platforms using this questionable gcc behaviour.

Details: https://svn.boost.org/trac/boost/ticket/6631