ntpd: add support for -I IFACE

function                                             old     new   delta
packed_usage                                       29908   29947     +39
ntp_init                                             428     460     +32
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 71/0)               Total: 71 bytes

Signed-off-by: Nikolaus Froehlich <nikolaus@mathematik.uni-marburg.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
udhcp: add PXELINUX path prefix option (code 210) definition

Like d3092c99, this change adds support for the DHCP "path-prefix"
option, as defined in RFC 5071. We use the string identifer
"pxepathprefix".

Adding this option makes string parsing in the hook scripts simpler.

function                                             old     new   delta
dhcp_option_strings                                  255     269     +14
dhcp_optflags                                         72      74      +2

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>