Convert init-script to procd and allow to configure
isc-dhcp-server via UCI. Allow most by-network and by-host options
supported by dnsmasq.
User-defined dhcp-options are not supported yet, neither are tags.

Existing configurations with use-edited /etc/dhcpd.conf are still
respected, hence to enjoy the new features you have to migrate
your configuration to UCI and delete /etc/dhcpd.conf.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

Version bumped to 4.3.5.  Separated out compile/install steps since
compiling with $DESTDIR yields bogus results. Removed rfc-3527 patch
as something similar (better) is now upstream (well, more complete
error checking anyway). Change relay scripts from '-l ifname' to
'-U ifname' to correspond to upstream changes.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

Signed-off-by: Antony Antony <antony@phenome.org>