Move library include to the top

This helps ensure that library inclusion is self sustainable

example/asymmetric/power.cpp

@@ -4,13 +4,14 @@
 //    (See accompanying file LICENSE_1_0.txt or copy at
 //          http://www.boost.org/LICENSE_1_0.txt)
 
+#include <boost/coroutine/all.hpp>
+
 #include <cstdlib>
 #include <iostream>
 
 #include <boost/bind.hpp>
 #include <boost/foreach.hpp>
 #include <boost/range.hpp>
-#include <boost/coroutine/all.hpp>
 
 void power( boost::coroutines::asymmetric_coroutine< int >::push_type & sink, int number, int exponent)
 {