prototyp: users_groups fixed: getpwent/getgrent needs setpwent/setgrent and endpwent/endgrent if we want to call them multiple times

prototyp: users_groups – buggy:

second run in UNION:
WARNING: SQL: XXX skupina je schizoidní 0
groups are not iterater for second time in one query (unioned)

Also this:
SELECT * FROM users; SELECT * FROM users;
returns weird results – first resultset is OK, second one is empty