Unwrap back_reference in get_pytype()

This prevents back_reference parameters from decaying to "object" in py signatures

include/boost/python/converter/pytype_function.hpp

@@ -9,7 +9,7 @@
 # include <boost/python/converter/registered.hpp>
 #  include <boost/python/detail/unwind_type.hpp>
 #  include <boost/python/detail/type_traits.hpp>
-
+# include <boost/python/back_reference.hpp>
 
 namespace boost { namespace python {
 
@@ -46,6 +46,12 @@ inline python::type_info unwind_type_id_(boost::type<T>* = 0, mpl::false_ * =0)
     return boost::python::detail::unwind_type<unwind_type_id_helper, T> ();
 }
 
+template <class T>
+inline python::type_info unwind_type_id_(boost::type<back_reference<T> >* = 0, mpl::false_ * =0)
+{
+    return boost::python::detail::unwind_type<unwind_type_id_helper, T> ();
+}
+
 inline python::type_info unwind_type_id_(boost::type<void>* = 0, mpl::true_* =0)
 {
     return type_id<void>();

test/map_indexing_suite.py

@@ -214,6 +214,13 @@
 ...     i.data()
 4
 
+#####################################################################
+# Test signature...
+#####################################################################
+
+>>> AMap.__iter__.__doc__.strip().split("\\n")[0]
+'__iter__( (AMap)arg1) -> __main__.iterator :'
+
 #####################################################################
 # END....
 #####################################################################