Changes to Mantle

Implemented per-command buffer atomic counter buffer operations for Mantle (grCmdSaveAtomicCounters, grCmdInitAtomicCounters)

Changes to amdilc

Handle AMD IL operations for atomic counter buffer (IL_OP_APPEND_BUF_ALLOC, IL_OP_APPEND_BUF_CONSUME) which are used by BF4.
Handle structured UAVs
handle atomic operations on structured and raw UAVs
handle atomic operations on structured and raw LDS
handle READ_ADD and READ_UMAX atomic operations for both LDS and UAV