Convert bitmap functions to use int32_t instead of int

Convert bitmap functions to use int32_t instead of int in data structures
and function arguments. This is to reliably enable use of bitmaps containing
up to 4 billion elements. Several data structures containing index values
were also changed from data type int to int32_t:
- Struct job_info / slurm_job_info_t: Changed exc_node_inx, node_inx, and
  req_node_inx from type int to type int32_t
- job_step_info_t: Changed node_inx from type int to type int32_t
- Struct partition_info / partition_info_t: Changed node_inx from type int
  to type int32_t
- block_job_info_t: Changed cnode_inx from type int to type int32_t
- block_info_t: Changed ionode_inx and mp_inx from type int to type int32_t
- Struct reserve_info / reserve_info_t: Changed node_inx from type int to
  type int32_t