udhcpc: account for script run time

Based on the following user report:

I ran into an issue where I was seeing a long delay in the scripts called
in udhcp_run_script. I was using an old version of OpenWrt (kamikaze)
and a satellite modem. An NTP script was being called and the modem
would sometimes take a long time to respond to the DNS lookup when
it was offline.

This delay started affecting my lease time. The lease that I would
get from my satellite modem before it was online would be short:
only 60 seconds. The delay with NTP and the modem would typically
be about 18 seconds. This would cause the first DHCP renew request
from dhcpc to be a little late. Under certain circumstances,
I could even see the first DHCP renew to occur after the lease
had expired!

function                                             old     new   delta
udhcpc_main                                         2816    2837     +21

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Make it possible to override LOGIN_FAIL_DELAY in CONFIG_EXTRA_CFLAGS

Signed-off-by: Peter Kümmel <syntheticpp@gmx.net>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
randomconfig fixes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
libbb: add sanity check in bb_arg_max()

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Bump version to 1.23.0

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Start 1.24.0 development cycle

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
udhcpd: account for script delay in lease

Prevent nasty surprises if script runs longer than lease time / 2.

Signed-off-by: John Schroeder <jschroed@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>