- Merge two functions for printing `id' output.

 - Merge two functions for printing `id' output.
   Showing the ids of both an user given by an argument to `id',
   and the current user, is now handled in a single function.
   Displaying the current user's ids was inaccurate because
   getgroups(2) had been used.  getgroups(2) returns the current
   kernel state of a user's groups, which may not always be
   correct if /etc/group was recently changed.
 - Fix a few style bugs.

PR:		bin/78085