Hash sc2::Unit pointer instead of UnitID

This is the result of some bug-hunting. But I don't know if it makes any
difference. It isn't worse, at least.

python-api-src/lib_unit.cpp

@@ -37,7 +37,7 @@ void define_unit(py::module & m)
         .def("build_target", &Unit::buildTarget)
         .def("train", &Unit::train)
         .def("morph", &Unit::morph)
-        .def("__hash__", [](const Unit & unit) { return std::hash<CCUnitID>{}(unit.getID()); })
+        .def("__hash__", [](const Unit & unit) { return std::hash<const sc2::Unit *>{}(unit.getUnitPtr()); })
         .def(py::self == py::self)
         .def("__repr__", [](const Unit & unit) { return "<Unit of type: '" + unit.getType().getName() + "'>"; });
 }