glsl: Translate atomic intrinsic functions on shared variables

glsl: Translate atomic intrinsic functions on shared variables

When an intrinsic atomic operation is used on a shared variable, we
translate it to a new 'shared variable' specific intrinsic function
call.

For example, a call to __intrinsic_atomic_add when used on a shared
variable will be translated to a call to
__intrinsic_atomic_add_shared.

v3:
 * Fix stale comments copied from SSBOs (Iago)

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>