add specific memory and semaphore enums for CL_DEVICE_HANDLE_LIST_KHR

[bashbaug]

see #864

Instead of reusing the same CL_DEVICE_HANDLE_LIST_KHR, adds a memory-specific CL_MEM_DEVICE_HANDLE_LIST_KHR, and a semaphore-specific CL_SEMAPHORE_DEVICE_HANDLE_LIST_KHR.

Reuses the same value for CL_MEM_DEVICE_HANDLE_LIST_KHR as discussed. The enum value for CL_SEMAPHORE_DEVICE_HANDLE_LIST_KHR is new, though.

[bashbaug]

Discussed in the August 1st teleconference:

• Remove the symbol name completely. Note that this will require rephrasing a few places that currently use the asciidoc dictionary entry.
• We will leave open another week or so for review.

[bashbaug]

I've made the changes to remove CL_DEVICE_HANDLE_LIST_KHR completely, as we discussed.

[bcalidas]

Looks ok

[nikhiljnv]

LGTM.

[nikhiljnv]

Merging as discussed on Aug 22 subgroup call.