- Make print_id a function rather than a macro.

- Make print_id a function rather than a macro.

- Update ID space for DO_SYS/DO_OTR to correspond to the IDs moira is
  now assigning.

- Include scary lookup table of all user and group pts ids that are
  inside the new "system" id space but aren't actually system users,
  i.e., they aren't tracked by moira.

  Potential future copious free time project: track this in an external
  config file the program reads.

- Visit from the decruftification fairy:
  * don't declare things we don't own.
  * replace sys_errlist with strerror().
  * modern function prototype/declarations.