Fix order of includes for Spirit scheme example. Changed iterator_range.size()

to use std::distance instead of subtracting iterators, this allows it to work
with iterators other than random access. Added more utree docs to Spirit.



[SVN r67153]

include/boost/range/iterator_range_core.hpp

@@ -230,7 +230,7 @@ namespace boost
 
             difference_type size() const
             {
-                return m_End - m_Begin;
+                return std::distance(m_End, m_Begin);
             }
 
             bool empty() const