glsl: Add new barrier functions for compute shaders

glsl: Add new barrier functions for compute shaders

When these functions are called in GLSL code, we create an intrinsic
function call:

 * groupMemoryBarrier => __intrinsic_group_memory_barrier
 * memoryBarrierAtomicCounter => __intrinsic_memory_barrier_atomic_counter
 * memoryBarrierBuffer => __intrinsic_memory_barrier_buffer
 * memoryBarrierImage => __intrinsic_memory_barrier_image
 * memoryBarrierShared => __intrinsic_memory_barrier_shared

v2:
 * Consolidate with memoryBarrier function/intrinsic creation (curro)

v3:
 * Instead of add_memory_barrier_function, add an intrinsic_name
   parameter to _memory_barrier (curro)

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>