Update clarifying comment.

slurm/slurm.h.in

@@ -418,15 +418,15 @@ typedef struct job_descriptor {	/* For submit, allocate, and update requests */
 	uint32_t min_sockets;	/* minimum number of sockets per node required
 				 * by job, default=0 */
 	uint32_t max_sockets;	/* maximum number of sockets per node usable 
-				 * by job, default=0 */
+				 * by job, default=unlimited (NO_VAL) */
 	uint32_t min_cores;	/* minimum number of cores per cpu required
 				 * by job, default=0 */
 	uint32_t max_cores;	/* maximum number of cores per cpu usable
-				 * by job, default=0 */
+				 * by job, default=unlimited (NO_VAL) */
 	uint32_t min_threads;	/* minimum number of threads per core required
 				 * by job, default=0 */
 	uint32_t max_threads;	/* maximum number of threads per core usable
-				 * by job, default=0 */
+				 * by job, default=unlimited (NO_VAL) */
 	uint16_t cpus_per_task;	/* number of processors required for each task */
 	uint16_t ntasks_per_node;/* number of tasks to invoke on each node */
 	uint16_t ntasks_per_socket;/* number of tasks to invoke on each socket */