forbid the include of GwHardware.h in user task headers

lib/hardware/GwHardware.h

@@ -11,6 +11,9 @@
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
+#ifdef _NOGWHARDWAREUT
+  #error "you are not allowed to include GwHardware.h in your user task header"
+#endif
 #ifndef _GWHARDWARE_H
 #define _GWHARDWARE_H
 #define GWSERIAL_TYPE_UNI 1

lib/usercode/GwUserCode.cpp

@@ -92,7 +92,9 @@ class GwUserCapability{
             userCapabilities[name]=value;  
         }
 };
+#define _NOGWHARDWAREUT
 #include "GwUserTasks.h"
+#undef _NOGWHARDWAREUT
 
 class TaskDataEntry{
         public: