Cycles: Pack kernel textures into buffers for OpenCL

Image textures were being packed into a single buffer for OpenCL, which
limited the amount of memory available for images to the size of one
buffer (usually 4gb on AMD hardware). By packing textures into multiple
buffers that limit is removed, while simultaneously reducing the number
of buffers that need to be passed to each kernel.

Benchmarks were within 2%.

Fixes T51554.

Differential Revision: https://developer.blender.org/D2745

intern/cycles/kernel/kernels/opencl/kernel_split_function.h

@@ -25,9 +25,7 @@ __kernel void KERNEL_NAME_EVAL(kernel_ocl_path_trace, KERNEL_NAME)(
 		ccl_global char *ray_state,
 		ccl_global uint *rng_state,
 
-#define KERNEL_TEX(type, ttype, name) \
-		ccl_global type *name,
-#include "kernel/kernel_textures.h"
+		KERNEL_BUFFER_PARAMS,
 
 		ccl_global int *queue_index,
 		ccl_global char *use_queues_flag,
@@ -52,12 +50,9 @@ __kernel void KERNEL_NAME_EVAL(kernel_ocl_path_trace, KERNEL_NAME)(
 
 		split_data_init(kg, &kernel_split_state, ccl_global_size(0)*ccl_global_size(1), split_data_buffer, ray_state);
 
-#define KERNEL_TEX(type, ttype, name) \
-		kg->name = name;
-#include "kernel/kernel_textures.h"
 	}
 
-	ccl_barrier(CCL_LOCAL_MEM_FENCE);
+	kernel_set_buffer_pointers(kg, KERNEL_BUFFER_ARGS);
 
 	KERNEL_NAME_EVAL(kernel, KERNEL_NAME)(
 			kg