add missing include

On 16.04, fix:
…/dynamic-graph-python-4.0.0/src/dynamic_graph/dynamic-graph-py.cc: In function 'void exposeCommand()':
…/dynamic-graph-python-4.0.0/src/dynamic_graph/dynamic-graph-py.cc:191:24: error: 'raw_function' is not a member of 'bp'
.def("__call__", bp::raw_function(dg::python::entity::executeCmd, 1), "execute the command")
^
8 jobs for pr/67 in 7 minutes and 41 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed doc-coverage #99067

00:03:08

66.0%
failed format #99068
allowed to fail

00:00:13

passed robotpkg-py-dynamic-graph-v3-py2-18.04-release #99063

00:03:57

passed robotpkg-py-dynamic-graph-v3-py3-16.04-release #99061

00:01:48

passed robotpkg-py-dynamic-graph-v3-py3-18.04-release #99062

00:03:12

passed robotpkg-py-dynamic-graph-v3-py3-20.04-release #99064

00:04:26

passed robotpkg-py-dynamic-graph-v3-py3-buster-release #99065

00:03:15

passed robotpkg-py-dynamic-graph-v3-py3-stretch-release #99066

00:07:40

 
Name Stage Failure
failed
format Test
   typedef SignalTimeDependent<T, Time> S_t;
- bp::class_<S_t, bp::bases<Signal<T, Time> >, boost::noncopyable> obj(
- name.c_str(), bp::no_init);
+ bp::class_<S_t, bp::bases<Signal<T, Time> >, boost::noncopyable> obj(name.c_str(), bp::no_init);
return obj;
}

Cleaning up file based variables
ERROR: Job failed: exit code 1