Implement paranoia mode.
* nscd/connections.c (nscd_init): Mark database and socket descriptors
as close on exec.
(restart): New function.
(restart_p): New function.
(nscd_run): Add missing descrement of nready in case readylist is
empty.
(main_loop_poll): Call restart_p and restart.
(main_loop_epoll): Likewise.
(begin_drop_privileges): Save original UID and GID.
* nscd/nscd.c: Define new variables paranoia, restart_time,
restart_interval, oldcwd, old_gid, old_uid.
(main): Disable paranoia mode if we are not forking.
(check_pid): When re-execing, the PID file contains the same PID as
the current process. Do not fail in this case.
* nscd/nscd.conf: Add paranoia and restart-interval entries.
* nscd/nscd.h: Define RESTART_INTERVAL. Declare new variables.
* nscd/nscd_conf.c: Parse paranoia and restart-internal configurations.
* nscd/nscd_stat.c: Print paranoia and restart-internal values.