Address spaces not listed for pointer argument of wait_group_events()

The description of **wait_group_events()** in the unified OpenCL specification does not list the valid address spaces for the `event_t *` pointer argument of this function.

For OpenCL _1.x_, and for OpenCL 3 _without_ the generic address space feature, it seems clear that this function takes a pointer to the private address space.

For OpenCL _2.x_ and for OpenCL 3 _with_ the generic address space feature, it is clear that pointers to the private address space must still be accepted, but it is not clear whether the pointers to the generic address space should also be accepted.

What are the required address spaces that must be supported for this function's pointer argument?

Start with the unified OpenCL specification entry for wait_group_events() and review the existing description of its event_t * argument across OpenCL 1.x, 2.x, and OpenCL 3. Determine the required address-space wording, then update the specification so the supported cases are explicit and verify the issue's question is answered.

Written by the indexing model from the issue text.