[boost] [spirit1] including type_traits.hpp

When looking at <http://thread.gmane.org/gmane.comp.lib.boost.devel/180769>, i noticed that <boost\spirit\home\classic\core\parser.hpp> includes <boost/type_traits.hpp>, when only part of it (remove_reference.hpp?) actually seems to be required. Not really a problem, but including the full type_traits.hpp does add quite a bit of weight to my precompiled header.