hostlist range format.

Fix example code in slurm_step_launch.3.

  slurm_job_step_launch_t -> slurm_step_launch_params_t
  slurm_job_step_launch_callbacks_t -> slurm_step_launch_callbacks_t

job_step_create_response_msg_t, and slurm_free_job_step_create_response_msg()
out of the SLURM API and hide them in the slurm protocol code.

Users will use the step context and step launch functions instead.

Permit the feature structure for nodes to be completely cleared (set to NULL not pointer to empty string).

will re-read any configuration files. Desired for wiki and 
wiki2. Likely required for gang.

    patch.1.2.0-pre10.061214.affinity_stepid from Dan Palermo (HP).

  could result in reading data too often.