Move slurm_step_layout_t struct to slurm.h.in so we can use it as the
returned object of a future API function.

altered the resource allocation and job_step_create_response structures.  Also altered the step_layout structure

Make NO_VAL for relative mean don't-use-relative offset.

--task-layout and --task-layout-file options.

Also have the slurmstepd set the SLURMD_NODENAME env variable.

something...

Remove debugging message.

requested.  For instance "slaunch -w foo[4,2,2,2,2,4,4] -n3" will only
launch 3 tasks on foo[4,2,2], and only asks the controller for foo[4,2,2].
If it asked for the whole string, scontroller would balk.

there are entries in the nodelist