made code proper to avoid warning/fixed some small potential bugs

confvirtualmot.c

@@ -71,7 +71,7 @@ static char *invokeMotorScript(pConfigurableVirtualMotor self,
     self->parseOK = 0;
     return NULL;
   }
-  return Tcl_GetStringResult(pTcl);
+  return (char *)Tcl_GetStringResult(pTcl);
 }