glsl: Handle compute shader local_size_{x,y,z} declaration.
WIP: update switch statements etc
WIP: implement generate_cs_special_vars()
mesa: Create the gl_compute_program struct, and the code to initialize it.
Fix another switch statement.
i965: Create the brw_compute_program struct, and the code to initialize it.
mesa: Implement MAX_COMPUTE_WORK_GROUP_COUNT constant.