Allow to show all process info using pcp_process_info, show pool_pools.

Allow to show all process info using pcp_process_info, show pool_pools.

  * it refactor "pcp processes info" related code to return all processes
  * info from backend, similar to the "show pool_pools" query
  * add pgpool process PID and backend id fields
  * add the ability to show all these informations from pcp_proc_info
  * command
  * no change to the pcp_proc_info command default behavior
  * new fields are added as last fields in the proc_info command only with
  * the -a switch (both verbose or not)

Patch contributed by Jehan-Guillaume (ioguix) de Rorthais