Fixed compilation with boost versions >= 1.56

source/RobotAPI/libraries/robotstate/remote/ArmarPose.cpp

@@ -379,8 +379,13 @@ namespace armarx
         ptree pt = Variant::GetPropertyTree(Vector3::writeAsXML());
         pt.add("frame", frame);
 
+        #if BOOST_VERSION >= 105600
+            boost::property_tree::xml_parser::xml_writer_settings<std::string> settings('\t', 1);
+        #else
+            boost::property_tree::xml_parser::xml_writer_settings<char> settings('\t', 1);
+        #endif
+
         std::stringstream stream;
-        boost::property_tree::xml_parser::xml_writer_settings<char> settings('\t', 1);
         xml_parser::write_xml(stream, pt, settings);
 
         return stream.str();