Copter 3.6 has only dropped support for gripper on boards that have a 1MB bug.
Does your board suffer from the 1MB hardware bug?
- Beta ArduCopter FW for Pixhawk1 boards with 1MB hardware bug (no gripper support, but all other goodies)
- Beta ArduCopter FW for Pixhawk1 boards without 1MB hardware bug (contains ALL features)
If you try to upload a full featured FW to a board with the 1MB hardware bug using Mission Planner, you will get an error. So try it out to see if you have the bug.
One other way to find out is: 1MB Flash space or not
And yes, you can enable gripper support on 1MB builds, but probably you will need to disable some other feature.