Remove unused deprecated includes

A comment in boost/iterator.hpp and boost/detail/iterator.hpp mentions that
the files are obsolete and will be deprecated. All they do is pull some types
from namespace std into namespace boost.

include/boost/iterator/iterator_facade.hpp

@@ -8,7 +8,6 @@
 #define BOOST_ITERATOR_FACADE_23022003THW_HPP
 
 #include <boost/config.hpp>
-#include <boost/iterator.hpp>
 #include <boost/iterator/interoperable.hpp>
 #include <boost/iterator/iterator_traits.hpp>
 #include <boost/iterator/iterator_categories.hpp>
@@ -37,6 +36,8 @@
 #include <boost/mpl/apply.hpp>
 #include <boost/mpl/identity.hpp>
 
+#include <cstddef>
+
 #include <boost/iterator/detail/config_def.hpp> // this goes last
 
 namespace boost {